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).



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.



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!

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)

[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.

[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.

[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]

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