Primer Blow Out with NO Over Pressure Signs?

[BuffCyclist]

Okay, so I went to the range today in hopes of finding the perfect load for my Rem 700 5R.

Caliber - 308 Winchester
Brass - Lake City LR 07 - Once Fired from brassbombers.com
Primer - Winchester Large Rifle
Powder - IMR-4064 - 38.0gr to 42.8gr in 0.4gr increments (13 loads and 5rds per load)
Bullet - Sierra MatchKing 168gr
Brass length - 2.005"
Case OAL - 2.800" (+/- 0.001 - I was shocked my Lee dies held this precision)
Barrel Length - 24"
Weather - 72*F, 5-7% humidity, 5mph wind gusts (ie dead calm)

Started shooting at 1rd of 38.0, 1rd of 38.4gr, 1rd of 38.8gr, etc shooting about 1 shot per minute. I was putting each round into the chamber by hand, not using the internal magazine (not that it matters). Shooting prone, off bipod, factory rifle/trigger with SWFA SS 10x MilQuad scope in TPS TSR 30mm rings (again, not that it matters).

First 12 rounds (38.0 to 42.4gr) went great. All were shooting about 1" left of the target, then I got to 42.8gr, which is lower than IMR max load by 2.3gr (IMR4064, 308Win, 24" barrel, 41.5gr at 2518 FPS to 45.9grC at 2766 FPS) and BOOM! Much more noise, tons of smoke and immediately I looked at my hands thinking the worst had happened and perhaps I had just had a kaboom. No blood, whew! Check out the rifle, looks okay, cycle the bolt.... cycle the bolt... shit. The bolt is stuck. I couldn't lift it up even a quarter inch.

Made sure the bullet went downrange (and saw the bullet impact), got up and was able to force the bolt up then with a different hold and a lot more force was able to pull the bolt back scraping a huge flap of skin off my pinky knuckle, hurts like hell, bled a lot. Pulled the bolt out of the gun and the brass was stuck in the face of the bolt. Ended up taking it to the range master to ask him if he had ever experienced that, he said no, and we proceeded to take pliers and pull the brass off the bolt face. That's when we saw the primer just fall out onto the floor. The face of the brass letters are partly flattened, though I think that's more from using the pliers at an angle (gripping case mouth and torquing it out). Here's a picture (42.0gr, 42.4gr, 42.8gr).

43447

The velocities for those 3 rounds were:
42.0gr = 2619 FPS
42.4gr = 2635 FPS
42.8gr = 2619 FPS (not sure if I believe this though)

As you can see, the primer is blown out. In fact, it has at least 0.04-0.06" play around the primer. The 42.0/42.4gr show only slight overpressure signs (round indent on 07 and LR), but those primers look perfectly fine, no cratering, no flattened edges, etc. After debating for a long time, looking at the rifle and it appearing fine in all functional tests I did, I decided this was a brass issue and that I'd keep shooting, perhaps avoiding the 42.8gr load.

Shot the 38.0gr load for the 2nd time and BOOM, same thing, only this time it doesn't lock up my bolt. Loads are 38.0gr on left, increasing to the right in 0.4gr increments. This 38.0gr load primer would fall out, but with quite a bit of smacking it on my hand, it was obviously loose but not as loose as the 42.8gr blow out.

43449

So here I sit with 51 rounds of ladder loads ready to shoot in brass that has questionably loose primer pockets (they all seemed fine as I was priming them). What is the best course of action? Pull them all and try a different LC LR brass year and scrap the 2007s? Pull them and load up brand new, high quality brass (like Win or Lapua)? Toss my hat into the ring and swear off reloading for the rest of my life? Give up guns entir... haha, just kidding! [LOL]

Here are the velocities I measured of 14rds I shot with a Competition Electronics Pro Chrono chronograph with brand new batteries.

38.0gr = 2351 FPS
38.4gr = 2376 FPS
38.8gr = 2389 FPS
39.2gr = 2415 FPS
39.6gr = 2464 FPS
40.0gr = 2487 FPS
40.4gr = 2482 FPS
40.8gr = 2515 FPS
41.2gr = 2569 FPS
41.6gr = 2583 FPS
42.0gr = 2619 FPS
42.4gr = 2635 FPS
42.8gr = 2619 FPS

38.0gr = 2287 FPS

According to the 308 Win Single Load Manual, with IMR-4064 in a 24" barrel, I should expect these velocities with the 168gr SMK.

37.8gr = 2400 FPS - Measured 2351 FPS
39.7gr = 2500 FPS - Measured 2464 FPS
41.5gr = 2600 FPS - Measured 2583 FPS
42.2gr = 2700 FPS - Measured ~2620 FPS

eta: Another question I have to ask, is do I need to be concerned that this did any permanent damage to my rifle, as in, do I need to ship it off to a gunsmith for inspection? (It'd go to BPTactical, I have no direct experience with him, but everything I've read on here, he's the one person I'd actually trust... Not to mention there are no reputable gunsmiths in the area).

[Jamnanc]

You've been doing it for longer than I have, but is there a possibility you got coal too long and they're engaging the rifling when you fired?

[BuffCyclist]

You've been doing it for longer than I have, but is there a possibility you got coal too long and they're engaging the rifling when you fired?

Thanks for the reply, I went to the IMR Load Data website to verify, but 2.800" is a standard length for 308Win ammo.

And while I haven't measured my rifle's distance from bolt face to rifling (tried, the result didn't make sense as I recall), I shot 20rds of Federal Gold Medal Match through my rifle when I was sighting in the scope and they were all exactly 2.800" +/- 0.0005" (not that I could measure that, but it was less than 0.001" variance)

43455

[XC700116]

First, There are PLENTY of pressure signs in that first picture, on the first 2 loads, flattened and cratered primers along with ejector marks. You really should have stopped at the 42 grain load. That said, The first things you should be doing from here on out is checking what your chamber allows for brass length, where your bullet is jumping or jaming, etc.

EVERY rifle and chamber are slightly different, then throw in COAL and if that puts you in a jump or jam with the bullet and then there's all sorts of variables, powder and primer lots, brass, etc. LC brass is typically much thicker than say Winchester brass and Fed GMM is well known for being on the hot side to the point of having loose primer pockets after the factory firing. Very seldom is book data going to align perfectly with a given rifle, brass, primer, bullet. There's far too many variables. I have a rifle that I can't get close to book max, and some that I can go well over with. it's a suggested guideline and that's all.

As to the rifle, if you don't feel confident to inspect it fully yourself, take it to a smith and have it looked over before putting more down the pipe.

[Great-Kazoo]

how many times has that brass been used? I didn't see or over looked that info. With loose pp's it could be the brass OR primers used. I'd try other brass, using same primers, and load data. IF it happened again, i'd be calling the mfg. maybe they had a load of mismarked LRM's ??

[BuffCyclist]

First, There are PLENTY of pressure signs in that first picture, on the first 2 loads, flattened and cratered primers along with ejector marks. You really should have stopped at the 42 grain load. That said, The first things you should be doing from here on out is checking what your chamber allows for brass length, where your bullet is jumping or jaming, etc.

EVERY rifle and chamber are slightly different, then throw in COAL and if that puts you in a jump or jam with the bullet and then there's all sorts of variables, powder and primer lots, brass, etc. LC brass is typically much thicker than say Winchester brass and Fed GMM is well known for being on the hot side to the point of having loose primer pockets after the factory firing. Very seldom is book data going to align perfectly with a given rifle, brass, primer, bullet. There's far too many variables. I have a rifle that I can't get close to book max, and some that I can go well over with. it's a suggested guideline and that's all.

As to the rifle, if you don't feel confident to inspect it fully yourself, take it to a smith and have it looked over before putting more down the pipe.

Thanks, I see that now after zooming in but in person, the cratering is not that obvious. I saw the ejector marks (round circle) but it wasn’t as prominent as I’ve seen online so didn’t think it was cause of too much concern (besides, the rim of the primer wasn’t flattened). And for what its worth, after seriously close inspection, I get that same cratering on ALL loads down to 40.0gr, but the ejector imprint starts at the 42.0gr load and up. (Derpa derp, 42.0gr IS at 2600 FPS, nevermind)

As far as checking out the rifle, is there anything specific that I should be checking for? It chambers, extracts loads just fine and the action is just as smooth as before.

[BuffCyclist]

how many times has that brass been used? I didn't see or over looked that info. With loose pp's it could be the brass OR primers used. I'd try other brass, using same primers, and load data. IF it happened again, i'd be calling the mfg. maybe they had a load of mismarked LRM's ??

Sorry, brass is once fired, range pickups from brassbombers.com.

Looking at the primers again, they are all marked WLR for Standard Loads.

[HoneyBadger]

Being a relative newb you can disregard everything I say if you want, but I agree with XC that there are pretty good pressure signs in your first loads.

Also, from what I understand, I wouldn't classify this incident as a "blown" primer. A true blown primer actually explodes (the face of the primer fails and the explosion comes out the back). It can leave debris in your firing pin channel and can damage your bolt face. I would call this more of a "loose" primer.

*My two cents*

[BuffCyclist]

Being a relative newb you can disregard everything I say if you want, but I agree with XC that there are pretty good pressure signs in your first loads.

Also, from what I understand, I wouldn't classify this incident as a "blown" primer. A true blown primer actually explodes (the face of the primer fails and the explosion comes out the back). It can leave debris in your firing pin channel and can damage your bolt face. I would call this more of a "loose" primer.

*My two cents*

Thanks HB, I won't lie, the "cratering" around the primers on those 3 cases in the first picture are easy to spot on the camera, but not so in person. They are seriously 0.002" if that. The same size ring is present in ALL charges from 39.6gr and up, and I highly doubt that it is a true overpressure sign unless 2415 FPS is the max velocity I can get with IMR4064 (39.2gr and no cratered primer) without pressure signs.

If this truly is primer cratering due to high pressure, why did the primer fall out on my 38.0gr charge, is that just from a loose primer pocket and a coincidence?

The question still remains, do I keep shooting the rest of these reloads, stopping at 41.6gr (setting 42.0gr as my max), or do I pull them and start over with brand new brass?

[Great-Kazoo]

pull and redo

[jerrymrc]

Something is not right. The proposed data and the measured data say one thing and the back end of those rounds say another. I have loaded 168 SMK's @ 2.800 in LC brass and run them as fast as 2600 with a warm load of 2460 and 2700fps with varget in a gas gun.

[BuffCyclist]

Something is not right. The proposed data and the measured data say one thing and the back end of those rounds say another. I have loaded 168 SMK's @ 2.800 in LC brass and run them as fast as 2600 with a warm load of 2460 and 2700fps with varget in a gas gun.

Care to expand or throw out some possible causes you might think of? Because this is what I was thinking too, that I shouldn't be getting these hot of loads at 2600 FPS. If I was closer to 2700, sure, it'd make sense.

Also forgot to mention, I applied a very light crimp with the Lee Factory Crimp Die (as in, factory ammo in ram, ram up, screw in die until touching case and that was my crimp). It barely did anything to the cases, so I highly doubt I crimped too much. I could always load up some more cases without the crimp stage and see what happens.

[jerrymrc]

Care to expand or throw out some possible causes you might think of? Because this is what I was thinking too, that I shouldn't be getting these hot of loads at 2600 FPS. If I was closer to 2700, sure, it'd make sense.

Also forgot to mention, I applied a very light crimp with the Lee Factory Crimp Die (as in, factory ammo in ram, ram up, screw in die until touching case and that was my crimp). It barely did anything to the cases, so I highly doubt I crimped too much. I could always load up some more cases without the crimp stage and see what happens.

Many will say never but I do crimp for the gas guns (lee FCD) but never for a bolt gun. Also never crimped the smk's for anything. Nowhere for the brass to go and not needed.

[BuffCyclist]

Many will say never but I do crimp for the gas guns (lee FCD) but never for a bolt gun. Also never crimped the smk's for anything. Nowhere for the brass to go and not needed.

Well then maybe therein lies my problem entirely. Could that be causing the extreme pressure without giving me the velocity expected with high pressure?

I guess I'll just pull all remaining loads, resize, reload with same powder after weighing charges again and load the same brass again without crimp and see what happens.

I didn't even think of the crimp, I crimp all of my other reloads and just did it out of habit, but I crimp so lightly I didn't think that would be a potential culprit (in other words, it is such a light crimp, that when I do pull the bullets, there won't be a crimp ring on them, I guarantee it).

[XC700116]

Care to expand or throw out some possible causes you might think of? Because this is what I was thinking too, that I shouldn't be getting these hot of loads at 2600 FPS. If I was closer to 2700, sure, it'd make sense.

Also forgot to mention, I applied a very light crimp with the Lee Factory Crimp Die (as in, factory ammo in ram, ram up, screw in die until touching case and that was my crimp). It barely did anything to the cases, so I highly doubt I crimped too much. I could always load up some more cases without the crimp stage and see what happens.

That very well could be what's causing your pressures. Any crimp on a bullet that doesn't have a cannalure for that purpose should not be crimped at all in a rifle. it takes very little crimp to cause a pressure spike in that situation.

[Zombie Steve]

Some possible reasons:

-You're jamming the bullet into the lands. Book data goes out the window when you do this.

- Your scale is off. Test with check weights.

- You thought you grabbed 4064 off the shelf, but it was some other number salad like 4895.


XC is right... all of those pieces of brass are telling you No Mas. Also, when you're adding powder but the speeds aren't increasing it's time to stop.

[Zombie Steve]

One other thing I thought of... you sure they weren't magnum primers?

[Great-Kazoo]

One other thing I thought of... you sure they weren't magnum primers?

I mentioned that before. perhaps a mismarked box of LRM instead of LRP. Plus he was doing .4gr increments, possibly a few extra grains made it through without being noticed.

[DSB OUTDOORS]

The 1st pic on the right looks like its a loose primer to begin with. Could be a Swager was not set up correctly. Or primer pocket reamed out to much. LC brass has a thicker webbing to the case and should be able to get 4 - 6 reloads out of them. Looks like you've done your homework as far as data goes.

[BuffCyclist]

Some possible reasons:

-You're jamming the bullet into the lands. Book data goes out the window when you do this.

- Your scale is off. Test with check weights.

- You thought you grabbed 4064 off the shelf, but it was some other number salad like 4895.

XC is right... all of those pieces of brass are telling you No Mas. Also, when you're adding powder but the speeds aren't increasing it's time to stop.

Thanks for the other possible places to look.

First, I was loading to 2.800. I don't know where the lands are, I tried the dowel method (dowel down bore to face of bolt, mark with knife, put loosely sized neck/bullet in chamber, slowly slide bolt forward but don't lock, put dowel down bore again and mark with knife) but when I did that I was getting almost exactly 2.8" and I did it a good dozen times. So either I wasn't doing it right, or the distance truly is 2.8 in which case I should have more than enough room before touching the lands.

I was checking the scale with my 20g check weight every time I changed charges and it never varied.

True, I do have IMR-4895 (only other rifle powder) but it is unopened and I just double checked, so the only powder I could have used was IMR-4064.


One other thing I thought of... you sure they weren't magnum primers?

Yes and no. The box says they are for Standard rifle loads, but that doesn't mean Winchester didn't put magnum primers in a standard box.


I mentioned that before. perhaps a mismarked box of LRM instead of LRP. Plus he was doing .4gr increments, possibly a few extra grains made it through without being noticed.

I was weighing every charge, not using a powder dropper, so no extra grains made it through.

___

I decided I was going to go pull 10rds (38.0-39.6gr) tonight and reprocess/weigh/seat/etc them but then I thought I’d look for a crimp first. Turns out, I did NOT crimp them. I bought the crimp die, thought about using it but then after researching it found that it isn’t necessary for bolt actions (usually) so I decided not to. Some people claimed they saw better accuracy when crimping for their bolts and I thought I could play with it down the road.

Here are 10 loads from this batch (UNcrimped) and one dummy round (CRIMPED). It is obvious the loads I shot today were not crimped. There is a slight ring, but that is from chamfering the outside of the case mouth when I trimmed.

43467

[BuffCyclist]

The 1st pic on the right looks like its a loose primer to begin with. Could be a Swager was not set up correctly. Or primer pocket reamed out to much. LC brass has a thicker webbing to the case and should be able to get 4 - 6 reloads out of them. Looks like you've done your homework as far as data goes.

Nope, that is the blow out I was talking about. That round is the one that locked up my bolt (after research tonight, locked/sticky bolt is due to overpressure and a very hot load) in which th eprimer just fell out. All of the cases primed as normal, none seemed light.

It's LC LR brass, so there is no crimp, it wasn't swaged or reamed. I only deprimed, cleaned, full length sized, cleaned (de-lube), then loaded.

[DSB OUTDOORS]

Nope, that is the blow out I was talking about. That round is the one that locked up my bolt (after research tonight, locked/sticky bolt is due to overpressure and a very hot load) in which th eprimer just fell out. All of the cases primed as normal, none seemed light.

It's LC LR brass, so there is no crimp, it wasn't swaged or reamed. I only deprimed, cleaned, full length sized, cleaned (de-lube), then loaded.
That could be part of the problem. All L.C. Military brass has a crimped primer pocket. I have swaged many, many, 5.56 and 7.62 so the brass you have has already been processed. Just a thought. Center pic. crimp, right some what removed, left removed.

43473

[Hoser]

That could be part of the problem. All L.C. Military brass has a crimped primer pocket.

LC Long Range ammo (LR-118) is not crimped.

[Hoser]

When brass flows into the ejector you are already pushing it. Primer cratering is not a very reliable indication of pressure.

[DSB OUTDOORS]

LC long Range ammo (118) is not crimped.
Ok fine then. [LOL] Just trying to help. [gohome]


So the problem still remains.................

[BuffCyclist]

Ok fine then. [LOL] Just trying to help. [gohome]


So the problem still remains.................

Yea, I kept trying to indicate it was LC LR but what can ya do [Tooth]

I mean, I guess I could have been maxed out but I expected to get to at least 2700 FPS with this 24" barrel when I hit max. After finding out I didn't crimp after all, it makes me go back to thinking it's either loose primer pockets, undersized primers (out of spec) or magnum primers, though with the magnums I would expect the velocities to be higher than what I got because they're in line with the powder loads and standard primer velocities.

[Zombie Steve]

Yea, I kept trying to indicate it was LC LR but what can ya do [Tooth]

I mean, I guess I could have been maxed out but I expected to get to at least 2700 FPS with this 24" barrel when I hit max. After finding out I didn't crimp after all, it makes me go back to thinking it's either loose primer pockets, undersized primers (out of spec) or magnum primers, though with the magnums I would expect the velocities to be higher than what I got because they're in line with the powder loads and standard primer velocities.

Your headstamp doesn't start looking like your bolt face because of crimp, undersized primers or loose pockets regardless of what speed you're getting. It's also unlikely they put mag primers in the box. The loads are overpressure plain and simple. My best guess is you're too close to the lands and some of the bullets' ogives are long / inconsistent and jamming the lands. As to speeds, some barrels are just slower than others. If it makes you feel better, my 168 target load averages 2,585 from a 24" Rem barrel and I'm not changing anything. You can try different combinations of components, but you can't tell the rifle what to like. It tells you.

[XC700116]

Thanks for the other possible places to look.

First, I was loading to 2.800. I don't know where the lands are, I tried the dowel method (dowel down bore to face of bolt, mark with knife, put loosely sized neck/bullet in chamber, slowly slide bolt forward but don't lock, put dowel down bore again and mark with knife) but when I did that I was getting almost exactly 2.8" and I did it a good dozen times. So either I wasn't doing it right, or the distance truly is 2.8 in which case I should have more than enough room before touching the lands.

I was checking the scale with my 20g check weight every time I changed charges and it never varied.

True, I do have IMR-4895 (only other rifle powder) but it is unopened and I just double checked, so the only powder I could have used was IMR-4064.



Yes and no. The box says they are for Standard rifle loads, but that doesn't mean Winchester didn't put magnum primers in a standard box.



I was weighing every charge, not using a powder dropper, so no extra grains made it through.

___

I decided I was going to go pull 10rds (38.0-39.6gr) tonight and reprocess/weigh/seat/etc them but then I thought I’d look for a crimp first. Turns out, I did NOT crimp them. I bought the crimp die, thought about using it but then after researching it found that it isn’t necessary for bolt actions (usually) so I decided not to. Some people claimed they saw better accuracy when crimping for their bolts and I thought I could play with it down the road.

Here are 10 loads from this batch (UNcrimped) and one dummy round (CRIMPED). It is obvious the loads I shot today were not crimped. There is a slight ring, but that is from chamfering the outside of the case mouth when I trimmed.

43467

I would agree on that, all the marked rounds are not crimped in that photo.

[XC700116]

When brass flows into the ejector you are already pushing it. Primer cratering is not a very reliable indication of pressure.

Yes, my LR rig will crater primers with very light loads and soft primer cups.


Also from what you said about tying to measure the OAL to the lands, I'd try loading a bunch, or just further seating the loads you have to 2.780 to make sure you're not jamming at all. If the pressure signs go away, you have your answer, but continue with caution.

[BuffCyclist]

Your headstamp doesn't start looking like your bolt face because of crimp, undersized primers or loose pockets regardless of what speed you're getting. It's also unlikely they put mag primers in the box. The loads are overpressure plain and simple. My best guess is you're too close to the lands and some of the bullets' ogives are long / inconsistent and jamming the lands. As to speeds, some barrels are just slower than others. If it makes you feel better, my 168 target load averages 2,585 from a 24" Rem barrel and I'm not changing anything. You can try different combinations of components, but you can't tell the rifle what to like. It tells you.

So then how do I explain the 38.0gr load (14th shot) that blew the primer out as well. that is 4.8gr lower than the over pressure load and did NOT show any signs of cratering, ejector marking, etc.

[BuffCyclist]

Yes, my LR rig will crater primers with very light loads and soft primer cups.


Also from what you said about tying to measure the OAL to the lands, I'd try loading a bunch, or just further seating the loads you have to 2.780 to make sure you're not jamming at all. If the pressure signs go away, you have your answer, but continue with caution.

But wouldn't seating the bullet 0.02" deeper cause other pressure signs?

[BuffCyclist]

Okay, so I decided to try the wood dowel method of measuring the bolt face to the lands again.

I seated a bullet in an empty case (FGMM once-fired in my rifle, BARELY sized the neck so it was a little tight but that I could easily push the bullet deeper by hand). Carefully put the round in the chamber, slowly slid the bolt forward until it stopped, then used a small bungee cord to hold it forward and up. Slid a wood dowel down the barrel until I touched the bullet and marked the dowel. Ejected the round carefully, then slid the bolt face forward again, bolt up, bungee and measured with the dowel again. Here are my measurements:

1 - COAL Before - 2.968"
1 - COAL After - 2.952"

Decided to fully close the bolt this time, and got nearly the same after measurement:
2 - COAL Before - 3.041"
2 - COAL After - 2.950"

Left the bolt in the up position again:
3 - COAL Before - 2.983"
3 - COAL After - 2.955"

I can continue doing this all day, but I have a feeling the COAL base to lands will be 2.950" +/- 0.01", so I have a feeling I am not jammed against the lands. And yes, while I don't have a way to measure the o-give yet by marking the bullet tip with sharpie and looking for the scratch mark from the rifling, it is at least 0.55".

The markings on the dowels are as follows:

1 - 3.015"
2 - 2.955" (closed bolt, not sure if this is accurate though)
3 - 3.016"
4 - 3.022"
5 - 3.010"

[Hoser]

But wouldn't seating the bullet 0.02" deeper cause other pressure signs?

Seating rifle bullets deeper causes the pressure to go down.

[BuffCyclist]

Seating rifle ammo deeper causes the pressure to do down, in rifles.

That is completely counter-intuitive (as long as the bullet isn't jammed against the lands). Seating it deeper means less case capacity, so when the primer ignites there is a smaller volume being expanded before pushing the bullet forward and before the powder ignites.

I've read a lot from you Hoser and know you are extremely knowledgeable on the subject, so I'll believe you, it just doesn't make sense.

I just googled it too and found an article by Barnes Bullets that corroborates this, but it also shows pressure spikes if the bullet is too far from the lands.

I have lots of time to figure this out, just found out my rifle is subject to the X-Mark Pro trigger recall, and sadly I don't have the funds for a brand new trigger right now so I think I'm going to have to ship the rifle back. :-(

[Zombie Steve]

In a 9mm case, seating deeper reduces case volume a lot. In a .308, your percentage of case volume barely changes at all. In a .30-06, even less. Big cases it just doesn't matter much. More important in rifles is that the bullet gets a running start at the lands. Keeps pressures down.

[BuffCyclist]

I've been researching this more (primer cratering) and found a source indicating that a dirty/fouled barrel can cause huge pressure spikes. The only thing here is that it isn't dirty. I cleaned the barrel when I got it (Hoppes #9, copper brush, patches, CLP) and have only put 20rds through it before yesterdays range day, so the 33rd round through the barrel blew out the primer, so I HIGHLY doubt that's the problem.

[TheBelly]

When brass flows into the ejector you are already pushing it. Primer cratering is not a very reliable indication of pressure.

Nail meet Hammer.

primer cratering is only indicative of one thing: there's a space in the bolt face for the striker to peek through and strike the primer. If there are pieces of the primer breaking/shearing off and ending up in the bolt, then that could be a problem.

my max load is 42.0 grains pushing a 175 gr bullet and a COAL of 2.805"

[TheBelly]

What's the max length from base of case to ogive that your rifle can handle?

[Hoser]

One more thing to consider...

Accuracy International rifles have a huge firing pin hole. With just about every mid range load and up, I get cratering.

May moons ago David Tubb blew up an SR-25 in 260 doing load development. The gun came apart but the brass/primer looked fine.

I measure case head diameter in extractor rim cut so I can tell if the pressures are high. Easier than measuring the insides of primer pockets.

[sako55]

It might be simple, but did you calibrate your scale?

[TheBelly]

Okay, so I decided to try the wood dowel method of measuring the bolt face to the lands again.

I seated a bullet in an empty case (FGMM once-fired in my rifle, BARELY sized the neck so it was a little tight but that I could easily push the bullet deeper by hand). Carefully put the round in the chamber, slowly slid the bolt forward until it stopped, then used a small bungee cord to hold it forward and up. Slid a wood dowel down the barrel until I touched the bullet and marked the dowel. Ejected the round carefully, then slid the bolt face forward again, bolt up, bungee and measured with the dowel again. Here are my measurements:

1 - COAL Before - 2.968"
1 - COAL After - 2.952"

Decided to fully close the bolt this time, and got nearly the same after measurement:
2 - COAL Before - 3.041"
2 - COAL After - 2.950"

Left the bolt in the up position again:
3 - COAL Before - 2.983"
3 - COAL After - 2.955"

I can continue doing this all day, but I have a feeling the COAL base to lands will be 2.950" +/- 0.01", so I have a feeling I am not jammed against the lands. And yes, while I don't have a way to measure the o-give yet by marking the bullet tip with sharpie and looking for the scratch mark from the rifling, it is at least 0.55".

The markings on the dowels are as follows:

1 - 3.015"
2 - 2.955" (closed bolt, not sure if this is accurate though)
3 - 3.016"
4 - 3.022"
5 - 3.010"


What is your magazine OAL?

[J]

Is the rifle 100% stock? Remmy almost always cuts their chambers LONG, to CYA on these types of things. At mag-length I still can't get my bullets as close to the lands as I would like (the 178 AMAX really likes to be 0.010 from the lands) I can get them to about 0,070 and keep it to the AI mag length.

Your chamber measurements are pretty close to what most find in stock Remmy chambers. I shoot a different bullet, so we can't compare apples to apples, but I'm at 2.954 COAL to be at the lands (measured with proper tools). Given the different bullet shape 2.950 sounds perfectly reasonable to me. Though the hornady tool to get a good measurement isn't terribly expensive and would probably be a good investment.

Go back to the low end and try a different batch of primers, powder and bullets and see what you get. It is possible something there was out of spec.

[J]

What is your magazine OAL?

In the B&C that comes on that, WAY too long. I bet he could get over 3.00 in there.

[TheBelly]

In the B&C that comes on that, WAY too long. I bet he could get over 3.00 in there.

Long enough to measure it and get it off the lands .002"?

[J]

If he were so inclined, yes. I'd advise him to get a better measurement before cutting it that close though.

[TheBelly]

I start with jammed into the lands, back it off .005" then find the powder node.

then mess with the jump.

[BuffCyclist]

Nail meet Hammer.


primer cratering is only indicative of one thing: there's a space in the bolt face for the striker to peek through and strike the primer. If there are pieces of the primer breaking/shearing off and ending up in the bolt, then that could be a problem.

my max load is 42.0 grains pushing a 175 gr bullet and a COAL of 2.805"

That’s what I was thinking. Honestly, the cratering I’m seeing is not the usual primer cratering, it is extremely minimal and somehow even the camera picked it up and magnified it.



What's the max length from base of case to ogive that your rifle can handle?

Can’t give you that, don’t have a method to measure the ogive yet, see further down.



One more thing to consider...

Accuracy International rifles have a huge firing pin hole. With just about every mid range load and up, I get cratering.

May moons ago David Tubb blew up an SR-25 in 260 doing load development. The gun came apart but the brass/primer looked fine.

I measure case head diameter in extractor rim cut so I can tell if the pressures are high. Easier than measuring the insides of primer pockets.

This sounds like something I should try to measure and see if there is any noticeable difference.

38.0 - .403 (2nd rd was .410 with the loose primer)
38.4 - .403
38.8 - .402
39.2 - .403
39.6 - .402
40.0 - .403
40.4 - .404
40.8 - .403
41.2 - .403
41.6 - .403
42.0 - .403
42.4 - .403
42.8 - .425 (not reliable because we pried this case out, but impressive)
Once fired case of same year - .404”

I measured the remaining 51 cases and they all measured 0.402-0.404”, so there are no signs of loose primer pockets on any of the other brass. While this method will work for determining after firing if the loads are hot, it does not appear to shed any light on what happened or if any of my other cases are compromised.



It might be simple, but did you calibrate your scale?

Yes, I checked it with my 20g check weight every 5 rounds between changing loads, and also used a 168gr SMK, 180gr pistol bullet and 124gr pistol bullet to confirm.



What is your magazine OAL?

Just measured that. It isn’t a magazine so to speak, but the hinged floor plate that comes stock on Rem 700s.

Rifle Magazine OAL - 2.830” (2.840” would not fit)
Measured by starting with a long case and load into internal magazine (hinged floor plate), then seat a 2.800” dummy round on top. Kept seating deeper until the 2.800” round would insert into the magazine.

I measured the overall length of a bullet again when seating to the lands and found it to be closer to 2.980", however, the bullet is barely held in there (anything longer than 3.010" and the bullet falls out if I look at it wrong).

I got this new measurement by seating bullet to 3.000 or longer, inserting into chamber softly, slowly sliding bolt forward and once the round was centered in the chamber (and not on the floorplate follower), push a dowel rod to touch the bullet. I would then hold the dowel rod loosely so I could feel it move as the bolt slid forward. I would softly tap the back of the bolt with my thumb and once I felt the dowel stop moving, I stopped tapping and pushed the round out slowly with the dowel.



Is the rifle 100% stock? Remmy almost always cuts their chambers LONG, to CYA on these types of things. At mag-length I still can't get my bullets as close to the lands as I would like (the 178 AMAX really likes to be 0.010 from the lands) I can get them to about 0,070 and keep it to the AI mag length.

Your chamber measurements are pretty close to what most find in stock Remmy chambers. I shoot a different bullet, so we can't compare apples to apples, but I'm at 2.954 COAL to be at the lands (measured with proper tools). Given the different bullet shape 2.950 sounds perfectly reasonable to me. Though the hornady tool to get a good measurement isn't terribly expensive and would probably be a good investment.


Go back to the low end and try a different batch of primers, powder and bullets and see what you get. It is possible something there was out of spec.

100% stock. The stock is a HS-Precision, not B&C.

Yes, I currently have these on the way:
Hornady LNL Bullet Comparator
Hornady LNL Overall Length Gauge (with modified case)
Hornady Headspace Gauge for 308 (to measure neck setback when I start neck sizing only)



In the B&C that comes on that, WAY too long. I bet he could get over 3.00 in there.

It’s an HS-Precision and I can fit 2.830” in the Rem hinged floor plate “magazine”.



Long enough to measure it and get it off the lands .002"?


If he were so inclined, yes. I'd advise him to get a better measurement before cutting it that close though.


I start with jammed into the lands, back it off .005" then find the powder node.

then mess with the jump.


So from here I should measure the overall length of the chamber, determine if I can get the bullet jammed (doubt I can and still have the neck tension to hold the bullet). I will also use the comparator to determine the case length from base to ogive and if I understand correctly:

Chamber length equals the measurement from the bolt face to rifling lands. Then, seat the bullet from case head to ogive to be the chamber length MINUS 0.005” (if possible).

Is there a way to determine the maximum length the round should be from case head to o-give for a given bullet? As in, how do I know if there is enough contact between the neck and bullet?



Also, I measured the diameter of some Win LR (WLR) primers and found them to be .210" and spec calls for .2105 minimum. While I don't have a pair of micrometers to measure to the half-thousanth, the needle on my calipers (Mitutoyo ie not Frankford Arsenal or Harbor Freight cheapies) was EXACTLY on .210" and not even a hair closer to .211".

[TheBelly]

Is there a way to determine the maximum length the round should be from case head to o-give for a given bullet? As in, how do I know if there is enough contact between the neck and bullet?





If you have the maximum OAL that your chamber can support, then you can get the 'jump distance' pretty easily.

Seeing as most dies don't load directly off the tip of the bullet, then you can take one round that's loaded to the correct length and just set your dies off of that. This is one of those times that I don't worry about the number too much, other than to make sure that the die doesn't move while I'm loading.

I can explain in better detail, but it takes a long time.

[BuffCyclist]

If you have the maximum OAL that your chamber can support, then you can get the 'jump distance' pretty easily.

Seeing as most dies don't load directly off the tip of the bullet, then you can take one round that's loaded to the correct length and just set your dies off of that. This is one of those times that I don't worry about the number too much, other than to make sure that the die doesn't move while I'm loading.

I can explain in better detail, but it takes a long time.

Thanks Belly, that part I understand. What I was trying to say is, is there a lookup table somewhere that shows the farthest out a bullet should be sticking from the case. As in, what is the minimum amount of contact with the case a bullet can have? Sort of like the book on ogives for all the bullets out there. Example, a 168gr SMK can not be longer than 2.85", a 175gr SMK can not be longer than 2.90", etc.

The rest of my tools should arrive today, but working 14hr days for the rest of this week and next, I won't have time to get to it for a while. I also ordered 100 brand new Lapua cases and will attempt to find some Federal 210 or CCI 200 primers locally. The plan is to pull the remaining 51 rounds, reweigh the charges to ensure they are what I was expecting, then using new primers and new brass, I will load them up again in the Lapua brass and reattempt shooting them at the range.

I am still not entirely sure the problem doesn't lie solely with the LC LR brass, because I have no other explanation (other than powder charges being off which I'll find out when I pull them) as to why the 38.0gr load had high enough pressure to unseat the primer immediately after the 42.8gr load really locked up my bolt. Unless I caused damage to the chamber and there is a crack pushing inwards tightening the chamber but I can't see that.

[TheBelly]

That engagement area rule won't exist in numbers relating to OAL, or at least it shouldn't. An OAL of 2.800 can have different amounts of engagement area based on trim length of brass. My trimmer trims from the neck. Therefore there'd be a different ratio of engagement area if a case is trimmed to 2.005 rather than the SAAMI spec of 2.015.

Here's a question: how would you measure (down to .001) the engagement area of a bullet that is loaded into a piece of brass? You can do it, but you'd have to use some arithmetic and critical thinking skills.

Yes, that's a challenge, and please show your work.

[BuffCyclist]

That engagement area rule won't exist in numbers relating to OAL, or at least it shouldn't. An OAL of 2.800 can have different amounts of engagement area based on trim length of brass. My trimmer trims from the neck. Therefore there'd be a different ratio of engagement area if a case is trimmed to 2.005 rather than the SAAMI spec of 2.015.

Here's a question: how would you measure (down to .001) the engagement area of a bullet that is loaded into a piece of brass? You can do it, but you'd have to use some arithmetic and critical thinking skills.

Yes, that's a challenge, and please show your work.

Yes, but if you are told the max length base to ogive for the 168gr SMK, it should show you the brass trim length. If it gives 2.015 and you use 2.005, then you will need to seat 0.010 deeper to get the same engagement between the bullet and brass/neck. What I'm trying to talk about is that if you trim all of your brass to the same length and seat the bullet to the same depth, you have the same contact area between the bullet and neck, so a pressure difference should not come into play there. However, if you use mixed brass and seat to the same OAL (or ogive length), you can have different pressure based on how much contact you have between brass/bullet. More contact logically equates to more pressure (more friction to overcome to unseat the bullet). But as my chief engineer says, logic is the art of being wrong with confidence. [LOL]

To calculate the engagement of the bullet, you need to use two ogive comparators and measure the ogive on the tip of the bullet to the ogive on the base of the same bullet (one comparator on bullet base, one comparator on bullet tip) and that gives you the bearing surface of the bullet. But then, you'll need to know the minimum engagement of that bullet. If I recall, I read somewhere that you need at least 1/3 of that bearing surface to contact the brass. 1/3 is a rough value and it would be better if there were a definitive value, unless 1/3 actually applies to all bullets regardless of their length and is simply 33% of that length.

In short, I'm trying to rule out ALL possible variations that cause pressure spikes.

Ahh, I see what you're saying now. You can't easily measure the amount of neck that is contacting the bullet. But, using the SAAMI geometry of the 308win case, you can get what it should be assuming you use the same length brass as the SAAMI specs. Then again, you can determine the length of the bullet's bearing surface (ogive to ogive) and then measure the distance from the ogive of the bullet to the lip of the case, subtract that value and that gives you the amount of bullet seated in the case. If you seat deeply, part of that will be below the neck and not contacting the brass, but that number could also be found quite easily (i think).

[TheBelly]

Now add in different frictional forces by the malleability of the brass at the neck.

[BuffCyclist]

Work:

http://upload.wikimedia.org/wikipedia/commons/4/49/Cartridge_308.PNG

Size/trim your brass to 2.015".
The engagement area = 2.015" - 1.7118 = 0.3032" ~= 0.303"

If you trim your brass to 2.005" your new engagement area is
engagement = 2.005" - 1.7118 = 0.2932" ~= 0.293"
0.2932 / 0.3032" = 0.9670 = 96.7%

So if you trim your brass to 2.005" then you have 3.3% LESS engagement and would need to modify your bullet seat depth accordingly to maintain the same contact and avoid pressure spikes from this.

This assumes your neck for each piece of brass is located at 1.7118", so you would need to measure each piece of brass and determine that.

[TheBelly]

So, how about case capacity: SAAMI spec vs. trimmed to 2.005 and that ratio as compared to the amount of volume that is taken up by the powder?

[BuffCyclist]

To determine how much the case capacity DECREASES when trimming to 2.005” instead of 2.015”, is quite simple:

Case capacity of top neck (2.015”) = pi*h*r^2 = pi*(2.015-1.7118)*((.3091/2)^2) = .02275 in^3
Case capacity of top neck (2.005”) = pi*h*r^2 = pi*(2.005-1.7118)*((.3091/2)^2) = .02200 in^3

This is assuming the top of the case
Difference = 0.00075 in^3 = 0.01229 cc

IMR-4064 VMD = .0745
VMD*charge = vol(cc)
1 cc = 0.0610237 in^3

Difference in Volume to Charge of IMR-4064 = 0.01229 cc / 0.0745 = 0.16496 gr
308 Win Published Case Capacity (2.015”) = 3.6 cm^3 = 0.21968 in^3

Ratio of case volume between 2.005" and 2.015" = (0.21968 in^3 - 0.00075 in^3) / 0.21968 in^3 = 0.99658 = 99.66%

Reduction in case volume by 0.34%

So, trimming to 2.005” vs 2.015” decreases the case volume by 0.00075 in^3. If you pack powder to the top of the case lip, using IMR-4064, the difference in powder charge is 0.16gr (assuming the VMD chart that Lee publishes is correct).

However, I argue that this is not accurate, since you will not be able to fill powder that high. Most powder charges (at least that I charge) stop at the base of the neck, so the amount of powder will not change. I do this to avoid compressed charges.


And if you had me work through this to show that by trimming to 2.005”, I had a pressure difference due to more powder in less space, then add the 0.66gr to 42.8gr and you get 42.96gr, which is BELOW IMR’s published data for max powder still by 2.14gr.


Oh, and Belly, I showed my work even though you didn’t tell me to. [Poke]

eta: Added case capacity as published on the 308 win wiki page.
eta2: Found a mistake, used case mouth diameter instead of case mouth radius, really changes the answer.

[Hoser]

Wow. All this time I have been trimming to min length or maybe a little less, sticking a bullet in 10-15 thou off the lands and calling it good.

My seat dies do not care how long my brass is. They reference the bottom of the case.

I prefer compressed charges. Lower ES and SDs normally results from it.

[BuffCyclist]

Wow. All this time I have been trimming to min length or maybe a little less, sticking a bullet in 10-15 thou off the lands and calling it good.

My seat dies do not care how long my brass is. They reference the bottom of the case.

I prefer compressed charges. Lower ES and SDs normally results from it.

Are you surprised at how little of a change you get when trimming to 2.005" instead of 2.015" or surprised at the depth Belly is making me analyze the situation? [LOL]

And for the record, this math is quite simple too so this level of analyzing isn't difficult. If I made a mistake, I retract my previous statement [LOL]

[BuffCyclist]

Work:

http://upload.wikimedia.org/wikipedia/commons/4/49/Cartridge_308.PNG



I just noticed this, comparing the above spec drawing and the measurements I obtained for my LC LR brass, the dimension of the groove for the extractor is 0.4091" and mine were measuring 0.404". Which indicates there is less material in the groove for the extractor on the LC LR brass (since the primer pocket has to be the same), so a near max pressure load will deform the LC LR brass EASIER (in that location) than if that dimension were to spec and was 0.4091". I will measure my Lapua brass when it arrives and see what it measures.

Not indicating this is the source of the problem as a difference in diameter of 0.0025" is not very much to be noticeably stronger, it is a discrepancy.

[TheBelly]

Are you surprised at how little of a change you get when trimming to 2.005" instead of 2.015" or surprised at the depth Belly is making me analyze the situation? [LOL]

And for the record, this math is quite simple too so this level of analyzing isn't difficult. If I made a mistake, I retract my previous statement [LOL]

hoser cutting in kinda ruined the fun.

I was waiting to see how much further you were going to play along until you realized that those changes don't matter that much. I poked you with a stick by using math to hook you in.

Bottom line: be consistent and try to make things the same. Certain measurements matter, others don't need to be worried about as much. The measurements I worry about are:

trim to length
distance from the lands
charge weight

[Hoser]

hoser cutting in kinda ruined the fun.


Thats cause Im a dick.

[BuffCyclist]

hoser cutting in kinda ruined the fun.


I was waiting to see how much further you were going to play along until you realized that those changes don't matter that much. I poked you with a stick by using math to hook you in.


Bottom line: be consistent and try to make things the same. Certain measurements matter, others don't need to be worried about as much. The measurements I worry about are:


trim to length
distance from the lands
charge weight


No no, I ENJOY math, I was doing that on my lunch break so I win. :P


I knew those measurements would be too insignificant to matter, but the math was easy and I was bored. But that’s precisely WHY I am still befuddled, because I trimmed all brass to 2.005” with my Wilson trimmer (brand new and worked perfectly), chamfered/deburred. They all were measured exactly the same and unless the ogive moved, the rounds were all within 0.005” of each other (closer based on bullet tip measurement but as we’ve established, that isn’t a standard measurement). The charge weight is what I was trying to nail down.


Sure, I will admit now that the 42.8gr charge was probably a little too hot (why the bolt didn’t even get slightly stick on 42.4gr I don’t know) but the charges were all double checked after recalibrating the scale so why did the 38.0gr charge blow out the primer. At this point, I am still leaning towards the primers being on the smaller side of the tolerance and loose primer pockets (faulty brass), combine the two and there you have it.

[BuffCyclist]

Allllllrighty, my Hornady Chamber Length gage and comparator have arrived and I finally have time to play around. Here's what I found.

Hornady Case = 2.007"
Comparator Gage Length = 1.005"

Out of 10 attempts, my averaged Chamber Length is
Base to Ogive = 2.3694"

After seating a bullet to that length and measuring:
Base to Tip (168gr SMK) = 2.949"

This makes sense, because I was measuring it at 2.950-2.952" before, but now I am more confident in the value.

So, I went back and measured/recorded all values for my remaining 51 rounds.
Average Base to Ogive = 2.2195"

2.3694" - 2.2195" = 0.1499"
2.949" - 0.1499" = 2.7991"

Which means my bullets are all seated to 2.799" (averaged) which is what I was aiming for before.

Now, with all of this in mind, I need to decide if I can seat a Sierra 168gr MatchKing to a length of 2.949" - 0.005" (0.005" off the lands) for a length of 2.944" or 2.364" (base to ogive) with my new Lapua brass. I still haven't tracked down any CCI #200 primers locally so I might try this again with the WLR primers and see if I get the same issues (only changing the brass and COAL).

After doing some math (can show work if needed/interested), I have found the bearing surface of the Sierra 168gr MatchKing bullet to be 0.500" ogive-to-ogive.

Tip of bullet to base ogive = 1.078"
Base of bullet to tip ogive = 0.632"
OAL of Bullet = 1.210"

1.210" - 1.078" = Base of bullet below base ogive = 0.132"
1.210" - 0.632" = Bullet above tip ogive = 0.578"
1.210" - 0.132" - 0.578" = 0.500"

So, my target OAL length (base to ogive) is 2.364"
Hornady Tool Case Length = 2.007"
Exposed bullet bearing surface (between ogive to ogive on bullet) = 2.364" - 2.007" = 0.357"
Therefore, my contact of brass to bullet = 0.500" - 0.357" = 0.143"
And finding the percentage = 0.143/0.500 = 0.286 = 28.6% contact.

This is less than the recalled value of 33% minimum contact surface between bullet to brass. The 33% value would mean my round OAL is
(.33/2) / 0.5 = 0.165
0.165" - 0.143" = 0.022"
0.022" + 0.005" = 0.027" away from the lands
2.949" - 0.027" = 2.922" COAL with Sierra 168gr MatchKing.

Alright, so that seems EXTREMELY long. I already know it won't fit into my rifles internal hinged floorplate magazine. But, is there a reason I should NOT load my next rounds to this length of 2.922"? I need to verify that the bullet to brass contact should be a minimum of 33% of the length of the bullet's bearing surface.

It looks like the AICS magazine max COAL length is 2.880". Since I plan to add a DBM at some point that uses AICS mags, should I load these rounds to 2.875", giving me a total of 0.074" away from the lands and 0.005" shorter than magazine max COAL?

Yes. I am probably overthinking this A TON! However, I want to make sure I don't have any more problems like that other time, even if as some of you said, I was seeing over pressure signs in my 42.0+ charges, even though it isn't the conventional primer cratering as I understand it.

[C Ward]

You want full bullet dia in the whole neck of the case . If not you end up with neck tension and run out issues .

The longest you want to go is where the boat tail ends or starts , depending on your viewpoint, even with the neck shoulder junction .

Don't worry about getting close to the lands with the factory chamber it will create more issues than benefits .

[BuffCyclist]

You want full bullet dia in the whole neck of the case . If not you end up with neck tension and run out issues .

The longest you want to go is where the boat tail ends or starts , depending on your viewpoint, even with the neck shoulder junction .

Don't worry about getting close to the lands with the factory chamber it will create more issues than benefits .

Is this a hard set rule or just a rule of thumb? I've seen this in a few places, but no one ever has a source, its just a "what I was told" type of thing.

Not sure if you read the rest of this thread or not, but I had serious problems at 2.800" length with these reloads, and am trying to eliminate possible sources of high pressure. I do not want to have my bolt lock up again and do not understand the precise source of the high pressure (since by now I think we've come to the conclusion that I did have high pressure).

eta:

Not to mention, the top of the shoulder according to the SAAMI spec drawing above is 1.7118”, add .308 and you’re at 2.0198”. This is beyond SAAMI’s max length, so that rule doesn’t make sense, nor is it even feasible in this situation.

[TheBelly]

If you can't move the bullet in the case with your bare hands, then there should be enough tension.

ive also heard of the 'one diameter' rule. If you load correctly, run out isn't that difficult to compensate/correct.

[<MADDOG>]

OP: have you tried factory loads? (If I missed it in my reading, my apologies in advance)

I hate to sound simplistic; but you guys are getting into brain surgery when it may be a mole.

[BuffCyclist]

OP: have you tried factory loads? (If I missed it in my reading, my apologies in advance)

I hate to sound simplistic; but you guys are getting into brain surgery when it may be a mole.

Thanks for the reply. Yes, I shot 20rds of Federal Gold Medal Match (168gr) to zero the scope, and then another 20rds of Black Hills Armory 175gr HPBT. They all shot perfectly. But then again, so did the first 12 of my reloads (1 shot each at charges from 38.0-42.4gr IMR4064, then 42.8gr locked the bolt, the primer fell out badly, shot the 2nd 38.0gr charge and same thing happened but no primer blow out).

And no, I don't think this is brain surgery. That would be me sending the rifle off to a gunsmith to just blueprint the entire brand new rifle. I haven't done anything else with it because I have some colleagues in town from Chile and have been attached to them about 12-14hrs per day the past 2 weeks. I am also waiting on new (Lapua) brass to arrive, which I will test the reloads with that again, so in the meantime, I am measuring everything possible and thinking of every single possible cause of the high pressure on the 42.8gr load and then the 38.0gr. My gut feeling is still telling me it was the brass.

[C Ward]

Yes I've read the whole thread , Hoser all ready said this once but since it seems to have fallen on deaf ears , the pressure problem is not from OAL it is from too much powder . For the OAL to cause a pressure issue in a rifle the bullet would need to be jammed into the lands . The peak pressure with a rifle round comes when the pressure spike happens when the bullet hits the lands and it builds until it over comes the resistance and pushes it down the bore . The closer to the lands the bullet is the sooner and faster this happens , increasing peak pressure

OAL is used to tune for accuracy not pressure . The chamber on that gun will not let you get 5 - 10 thou from the lands with ammo that will be reliable so it makes no since to compromise the reliability of the ammo to load it long . The Match King bullets are very jump tolerant and distance from the lands is a non issue .

99 times out of 100 too much pressure equals too much powder , back the powder charge down . Brass is simply a container for the combustion process and the only affect it has on the pressure is the space available inside for it to happen . Also as of late Lapua brass has had less case capacity then the newer LC brass so the powder charge will need backed down even more .

[BuffCyclist]

Yes I've read the whole thread , Hoser all ready said this once but since it seems to have fallen on deaf ears , the pressure problem is not from OAL it is from too much powder . For the OAL to cause a pressure issue in a rifle the bullet would need to be jammed into the lands . The peak pressure with a rifle round comes when the pressure spike happens when the bullet hits the lands and it builds until it over comes the resistance and pushes it down the bore . The closer to the lands the bullet is the sooner and faster this happens , increasing peak pressure

OAL is used to tune for accuracy not pressure . The chamber on that gun will not let you get 5 - 10 thou from the lands with ammo that will be reliable so it makes no since to compromise the reliability of the ammo to load it long . The Match King bullets are very jump tolerant and distance from the lands is a non issue .



There are no deaf ears, and no need for sarcasm or getting aggressive. I am taking all input I can receive and examining every possible source.

Precisely, the OAL comes into play when at the lands. So, jam the bullet to the lands or get extremely close, work up my loads THERE and then when I seat deeper I will not have pressure issues due to jamming.



99 times out of 100 too much pressure equals too much powder , back the powder charge down . Brass is simply a container for the combustion process and the only affect it has on the pressure is the space available inside for it to happen . Also as of late Lapua brass has had less case capacity then the newer LC brass so the powder charge will need backed down even more .

If you firmly believe the over pressure signs I saw were from too much powder, then please, explain to me how the primer blew out on the 38.0gr charge when I can guarantee it had 38.0 +/-0.02gr of IMR-4064. That is 4.8gr LOWER than the charge where I had the primer blow out on as well, including the ejector marks on the case head and totally locked up bolt (bolt wasn't even sticky at 42.4gr and I know sticky bolts, my 22LR bolt rifle is difficult to cycle, but my Rem7005R can be operated with my pinky, which I do while shooting because its easy and doesn't disturb my sight picture as much). The 38.0gr charge primer blew out and will slip in/out of the case now. That case does NOT have the ejector imprint.

Yes, I admit that 42.8gr might be too much powder. But I can not explain logically or scientifically why the 38.0gr charge blew out the primer either. If all I had was the primer blow out on the 42.8gr load, then I would not be as hesitant or careful with altering my loads and continuing forward. As it is now, I would be lying if I said I wasn't somewhat hesitant to pull the trigger again on that rifle, even at the 38.0gr charge. Again, I am leaning towards it being a brass issue - loose primer pockets - or a primer issue - slightly undersized primer cup. Until I can eliminate these two variables, I can not rule out any other variable and while I wait for my brass to ship, I am researching in every free second I have.

I also haven't found anywhere that has said explicitly with evidence that loading 308Win to 2.944" (0.005" off my lands) will cause problems. Nearly everyone says to load to magazine length and be done with it. But precision shooters say to start at the lands and back off when WORKING UP POWDER LOADS (granted, working up powder loads IS done for accuracy, ... ). Yes, this rifle is NOT a GAP, Surgeon or other precision built rifle and has a very long chamber. But concentricity is easy to measure/compensate, as Belly said and confirmed by my research, so seating the bullet out to 2.944" with only 28.6% bullet bearing surface contact with the brass should not cause problems as long as it is concentric, or within 0.002" (as much as 0.003" out of concentric will cause accuracy issues, NOT over pressure issues).

eta: If I feel the need to model up my rifle action and perform a fluid dynamical FEA analysis on it, I will do so until I am satisfied. It simply means I wouldn't be able to shoot my rifle again until next year due to my limited time to work on this.

[20X11]

Flattened, loose primers also happen from excessive headspace (improperly adjusted dies setting the shoulder back too far). I read the whole post but haven't seen this mentioned or verified.

[BuffCyclist]

Flattened, loose primers also happen from excessive headspace (improperly adjusted dies setting the shoulder back too far). I read the whole post but haven't seen this mentioned or verified.

No idea on this, I haven't tried measuring my rifles headspace. I used Lee Full Length sizing die to size all brass initially before trimming everything to 2.005". I also wouldn't say my primers were flattened, just loose. The 42.8gr has a good 0.025" movement around the primer. The 38.0gr load doesn't have wiggle room, but it will slip out easily.

[C Ward]

The load data in the book is only for that particular component combination and that particular test rifle . Every other rifle and set of components will be different, the book is a guide not the law .

15 years of loading for precision rifles experience tells me your headed down the path to ammo issues . In the end your gonna do whatever you want , the whole lead a horse to water thing , have fun .

[BlasterBob]

I probably shouldn't be making ANY comments in this rather scientific reloading discussion and I have not read each and every post in this thread but someone mentioned that perhaps the swaging was not proper. I thought LR and Match cases did not have the primer pockets crimped so surely swaging would have nothing to do with this matter.

[BuffCyclist]

The load data in the book is only for that particular component combination and that particular test rifle . Every other rifle and set of components will be different, the book is a guide not the law .

15 years of loading for precision rifles experience tells me your headed down the path to ammo issues . In the end your gonna do whatever you want , the whole lead a horse to water thing , have fun .

Exactly. IMR states starting load of like 41gr, max 45gr. Another manual said 38gr-42gr. So that was problems in and of itself.

[BuffCyclist]

I probably shouldn't be making ANY comments in this rather scientific reloading discussion and I have not read each and every post in this thread but someone mentioned that perhaps the swaging was not proper. I thought LR and Match cases did not have the primer pockets crimped so surely swaging would have nothing to do with this matter.

Precisely and this has already been brought up.

Eta. On phone and can't talk much. This has been brought up as a possible cause buy it is long range brass and is not crimped.

[TheBelly]

OAL is used to tune for accuracy not pressure . The chamber on that gun will not let you get 5 - 10 thou from the lands with ammo that will be reliable so it makes no since to compromise the reliability of the ammo to load it long . The Match King bullets are very jump tolerant and distance from the lands is a non issue .

99 times out of 100 too much pressure equals too much powder , back the powder charge down . Brass is simply a container for the combustion process and the only affect it has on the pressure is the space available inside for it to happen . Also as of late Lapua brass has had less case capacity then the newer LC brass so the powder charge will need backed down even more .

doesn't pressure change when you have more/less case capacity? Can't case capacity change due to the amount of bullet seated into the case? (I'm not trying to be a jerk, just seeking clarification on this point.)

[BuffCyclist]

doesn't pressure change when you have more/less case capacity? Can't case capacity change due to the amount of bullet seated into the case? (I'm not trying to be a jerk, just seeking clarification on this point.)

Yes but it is the percentage of change. The minimal amount the case capacity would decrease when seating deeper is so small, my understanding is that it won't affect the pressure as greatly as say on a pistol. on pistol, sear deep and you have more bearing surface. On rifle, ar one point the bullet bearing surface will be below the shoulder and not affect the friction required to unseat the bullet. On phone so can't be clearer than that lol

[TheBelly]

Yes but it is the percentage of change. The minimal amount the case capacity would decrease when seating deeper is so small, my understanding is that it won't affect the pressure as greatly as say on a pistol. on pistol, sear deep and you have more bearing surface. On rifle, ar one point the bullet bearing surface will be below the shoulder and not affect the friction required to unseat the bullet. On phone so can't be clearer than that lol

my questions wasn't in reference to bearing surface, but rather about the physical volume taken up by the projectile as it is seated at different depths. The volume occupied by the bullet changes the percentage of available volume, and thus can change the pressure curve... Is that mathematically possible, BC?

[BuffCyclist]

my questions wasn't in reference to bearing surface, but rather about the physical volume taken up by the projectile as it is seated at different depths. The volume occupied by the bullet changes the percentage of available volume, and thus can change the pressure curve... Is that mathematically possible, BC?

Yes, but the volume that changes is minimal so it won't affect it.

[BuffCyclist]

Just when everyone thought this thread was buried, here's more DATA!!! [LOL]

I measured the chamber length with 15 different bullets, then averaged the results.

Actual Length (base to ogive) = 2.3655"
Chamber Length = 2.9455"
Average Bullet Bearing Surface (ogive to ogive) = 0.5025"
Average Base to Ogive - 0.005" back from Lands = 2.3605"
Average COAL - 0.005" back from Lands = 2.9405"

Amount of bullet bearing surface below brass lip (bullet to brass contact) = 0.1490" = 29.65%

I then seated 5 bullets to a length of 2.3605" base to ogive and attempted to unseat the bullet by hand for about 1min each bullet. I then measured again and was unable to determine a change in length of any of the 5 bullets. Which makes me believe that seating the bullets this long does not make fragile-as-eggs ammo. After that, I chambered each bullet, closing the bolt hard, then remeasuring and again, could not detect the bullet seating deeper (due to touching the lands).

If the only problems I will have in seating the ammo this long is the internal hinged floorplate magazine length, then perhaps I will load up to this length when I get my Lapua brass (if SWA ever ships it) and retest.

On the other hand, I just found Alpha Industries Type 1 Magazine (an AICS pattern magazine) and they claim a max COAL of 2.920". If I seated to this depth, I would be 0.020" back from the lands.

Or, I could seat to 2.880" length which AICS mags, and be 0.045" back from the lands.

The options are endless!!

[Zombie Steve]

Flattened, loose primers also happen from excessive headspace (improperly adjusted dies setting the shoulder back too far). I read the whole post but haven't seen this mentioned or verified.

Sorry, haven't checked into this thread in a while...

Yes, if you're pushing the shoulder too far and it's a light load, the primer can pop out. Several things at play... primer goes off and jumps out of the pocket. Normally the powder charge then expands the case and the primer re-seats flush with the base (we're talking fractions of a second here). With a light load and a headspace problem, there's too much room between the brass (that doesn't expand enough due to the light load) and the bolt face... potentially enough for the primer to come totally out. That explains the 38.0 grain load. I discovered this early on with start loads ridiculously low in Hornady #7.

Headspace problem plus powerful load usually means case head separation (almost always a headspace problem).

Forget what came with your die set. Normally, you can turn the sizing die down until it touches the shell plate and you're good to go. Most directions say to go 1/8 to 1/4 beyond that so it cams over. I have found this to be detrimental with autoloaders (bolt guns I just neck size, so it's never an issue). A case gauge is very much worth the money.

My only other advice is don't load to 42.8 grains. Find a different powder / bullet / primer / brass combination if it's not doing what you want.

[BuffCyclist]

Sorry, haven't checked into this thread in a while...

Yes, if you're pushing the shoulder too far and it's a light load, the primer can pop out. Several things at play... primer goes off and jumps out of the pocket. Normally the powder charge then expands the case and the primer re-seats flush with the base (we're talking fractions of a second here). With a light load and a headspace problem, there's too much room between the brass (that doesn't expand enough due to the light load) and the bolt face... potentially enough for the primer to come totally out. That explains the 38.0 grain load. I discovered this early on with start loads ridiculously low in Hornady #7.

Headspace problem plus powerful load usually means case head separation (almost always a headspace problem).

Forget what came with your die set. Normally, you can turn the sizing die down until it touches the shell plate and you're good to go. Most directions say to go 1/8 to 1/4 beyond that so it cams over. I have found this to be detrimental with autoloaders (bolt guns I just neck size, so it's never an issue). A case gauge is very much worth the money.

My only other advice is don't load to 42.8 grains. Find a different powder / bullet / primer / brass combination if it's not doing what you want.

Now this actually makes sense. I have a headspace insert for my hornady comparator, so I'll measure up some brass tonight and see where its at. I used the Lee Full Length sizer, so I have no idea what the shoulder is at. I needed to fire form this brass before I could use my Lee Collet Sizer, and I don't recall what I did with the die setup, if I touched the shell plate, turned 1/8-1/4 more. I most likely followed the Lee directions.

I was just telling Belly in a PM, I'll probably load them to 2.825" (internal mag length is 2.835") and do another ladder test, starting at 39.0gr (or even higher) and working up to 42gr. Especially since 38.0-39.6gr was 2351 FPS - 2464 FPS, which is slower than I want to go, so I might as well save powder/bullets. That is, using the new Lapua brass and possibly other primers if I can find any in stock locally. I'm taking some WLR primers with me to work today to measure them with mics to see if they are truly undersized or within spec. If they're undersized, I might try calling Win and asking why they're undersized.

[TheBelly]

PM Returned.

I think we can change a couple things around to continue being nerds abotu this stuff that most likely doesn't matter.

[Zombie Steve]

Now this actually makes sense. I have a headspace insert for my hornady comparator, so I'll measure up some brass tonight and see where its at. I used the Lee Full Length sizer, so I have no idea what the shoulder is at. I needed to fire form this brass before I could use my Lee Collet Sizer, and I don't recall what I did with the die setup, if I touched the shell plate, turned 1/8-1/4 more. I most likely followed the Lee directions.

I was just telling Belly in a PM, I'll probably load them to 2.825" (internal mag length is 2.835") and do another ladder test, starting at 39.0gr (or even higher) and working up to 42gr. Especially since 38.0-39.6gr was 2351 FPS - 2464 FPS, which is slower than I want to go, so I might as well save powder/bullets. That is, using the new Lapua brass and possibly other primers if I can find any in stock locally. I'm taking some WLR primers with me to work today to measure them with mics to see if they are truly undersized or within spec. If they're undersized, I might try calling Win and asking why they're undersized.

Amendment to my previous post - I shouldn't have said brass expanding (it does, but shouldn't much if it's sized right) - the powder charge going off pushes the brass back against the bolt face and essentially re-seats the primer.

[BuffCyclist]

FINALLY, I HAVE SOME ANSWERS!!! [WooHoo]

Was distracted this morning when I showed up to work, my chief engineer asked me what I was thinking so hard about, so I told him. He took me out to the machine shop and after searching high and low for about 10-15min, finally found them and handed me a pair of Starrett Small Hole Gages and a pair of Starrett Micrometers (0.0001" precision). Told me to borrow them for the night and I'd have my answer, whether it was out of spec primers or out of spec primer pockets in the brass.

So, as soon as I got home, I started measuring. What did I find? Well let me tell you!


I found the specs for primers as well as primer pockets ( http://ballistictools.com/articles/primer-pocket-depth-and-diameter.php ) and started measuring 10 each of LC LR 07 primer pockets, CCI BR2 LR primers, WLR primers, and some other misc brass.


All of this data was taken from measuring between 10-20 cases/primers, and recording the measurement 3 times, the writing down the average of those 3 for all cases/primers. The same measurements between cases were VERY consistent.

LR Primers
Min = 0.2105"
Max = 0.2130"

LR Primer Pockets
Min = 0.2085"
Max = 0.2100"

CCI BR2 Primers - 0.2111" (middle of spec)
WLR Primers - 0.2103 (lower end of spec)

LC LR 04 Primer Pockets - 0.2094" (in spec)
LC LR 07 Primer Pockets - 0.2106" (above spec)
LC LR 08 Primer Pockets - 0.2097" (in spec)
LC LR 10 Primer Pockets - 0.2100" (max spec)
LC LR 11 Primer Pockets - 0.2095" (in spec)
R-P Primer Pockets - 0.2098" (in spec)
Black Hills Primer Pockets - 0.2100" (max spec)

I STILL don't have the Lapua brass, not happy with SouthwestAmmunition for that, they were in-stock when I ordered, then they claimed they must have sold out after I ordered even though the page still hasn't changed like some other items that say "Requires an additional 1-2 weeks processing time)". Anyways, I don't have that brass in yet so I can't measure the primer pockets to see what they are.

What I think happened is that the LC LR 07 primer pockets were a few ten thousandths (as in, as much as 0.0003"-0.0005") larger than the primers, which caused less friction to hold the primer in place, so the primers were easier to unseat and blow out. When I get time, I'll be pulling the remaining 51rds, weighing charges to ensure that wasn't a contributing factor too but will then just load up the Lapua brass with a smaller range of powder charge and retest.

Oh and my Timney Trigger arrives today to fix the XMark Pro Trigger Recall problem. So that should be fun.