Piercing primers

[MattR]

Ok so I built a gas piston upper with an Osprey conversion on a 16" bbl and a mid length gas system, it has 60 rounds of commercial ammo cycled through it for function testing and break in. I tried my reloads in it which are new remington and winchester brass, cci primers, 26gr of Varget, and 55gr bullets not crimped just pressed in with the die. Now the commercial rounds no pierced primers, my reloads all 12 pierced the primers. Too hot one would say, but I checked the reloads in a rifle length GI system and no pierced primers and no signs of too much pressure. All tests made were with the same lower with a RR 2 stage trigger. I'm lost any ideas would be helpful. Thanks

[BPTactical]

Ok so I built a gas piston upper with an Osprey conversion on a 16" bbl and a mid length gas system, it has 60 rounds of commercial ammo cycled through it for function testing and break in. I tried my reloads in it which are new remington and winchester brass, cci primers, 26gr of Varget, and 55gr bullets not crimped just pressed in with the die. Now the commercial rounds no pierced primers, my reloads all 12 pierced the primers. Too hot one would say, but I checked the reloads in a rifle length GI system and no pierced primers and no signs of too much pressure. All tests made were with the same lower with a RR 2 stage trigger. I'm lost any ideas would be helpful. Thanks


I am not familiar enogh with reloading but STOP SHOOTING YOUR RELOADS immediatley.


Not crimping the the reloads could be key here. Like I said I dont know much about reloading but if I am not mistaken when you crimp the bullet a couple of things happen:
1-The bullet is seated a bit deeper in the case.
2-The crimp provides a bit of a taper for the "Leade" of the chamber. The leade is the unrifled portion of the chamber where the bullet is. It provides a head start for the round when fired before the bullet enters the rifling. Some people call it the "Throat" of the chamber. If the round is crowded into the rifling you will get a pressure spike.
The uncrimped neck could possibly be crowding the round a bit and spiking.

With this not happening with the other upper the converion could be suspect. Maybe not venting pressure quite as quickly as a GI system causing a pressure spike.
You get a quicker gas impulse with a 16 than you do a 20.

Have you checked the headspace? The chamber could be a smidge short.
Have you checked the firing pin protrusion? .028 minimum .036 maximum.

Let us know-I am curious what you find out as I know damn little about re-loading.

[USMC88-93]

Correct me if I'm wrong but shouldn't you work your reloads up on each rifle you use and not presume that your reloading recipes will work in every weapon? That sounds like a lot of Varget based on my limited exposure to reloading for 75gr but I am not familiar with the min and max for your weight of bullet.

[spencerhenry]

i am not claiming to be an expert about reloading, but i have loaded tens of thousands of rounds in numerous calibers. i have never heard nor seen any indication that not crimping a bullet would cause that issue. there is also NO reason to indicate that a crimped bullet would be seated deeper. seating depth while using a crimp is limited to where the cannelure is, but that does not mean that if uncrimped the bullet is seated shallower. almost none of the bullets i load for rifle calibers have a cannelure.

if you are piercing primers, there could be a few different issues. military ammo is known to have thicker primer cups, commercial may as well depending on the manufacturer, primers for reloading could have thinner cups. your firing pin could be "sharp" or could be protruding too far, switch out the pin, or the entire bolt from a gun that doesnt pierce the primer. do you have other signs of high pressure? check the case heads for expansion with a micrometer compared to the unfired round. if the rifle is over gassed, or the bolt is opening too soon, the more likely result is expanded case heads. does the headstamp have shiny spots, or is the rim bent from the extractor? those would be signs of the bolt opening under pressure. is the primer flattened or set back against the bolt face? that could mean high pressure.
first thing i would do is compare firing pins from the two different uppers, if you are using the same firing pin, then i would start looking at pressure problems. i have never had a primer pierce, but i have definitely loaded some maximum to slightly over maximum loads. does the loading manual where you got this load recommend a magnum or standard primer? it isnt a pistol primer right?

[MattR]

I forgot to mention the chamber is the Wylde chamber, I thought about the firing pin being sharp so I put a new one in it and same thing. My guess is that the carrier tilts as it cycles because there is a sign of wear on the buffer tube and hangs up just long enough to spike the pressure. I'm going to try a different tube and then go back to the GI and see what happens.

[CTN]

Here is some information from a very good black rifle smith that has a shop in Pueblo West.

http://www.68forums.com/forums/showthread.php?t=16256

[OgenRwot]

I am not familiar enogh with reloading but STOP SHOOTING YOUR RELOADS immediatley.


Not crimping the the reloads could be key here. Like I said I dont know much about reloading but if I am not mistaken when you crimp the bullet a couple of things happen:
1-The bullet is seated a bit deeper in the case.

This is not true, the seating depth has nothing to do with crimping. You can seat your bullet as deep as you want, crimp or no crimp.

2-The crimp provides a bit of a taper for the "Leade" of the chamber. The leade is the unrifled portion of the chamber where the bullet is. It provides a head start for the round when fired before the bullet enters the rifling. Some people call it the "Throat" of the chamber. If the round is crowded into the rifling you will get a pressure spike.

This is not necessarily true. Lots of people seat into the lands.

The uncrimped neck could possibly be crowding the round a bit and spiking.

Again, this has nothing to do with crimping, it has everything to do with seating depth. But if he's seating his rounds deep enough to fit in the magazine he's not going to be pushing the bullet into the lands. If it was crimped and hitting the lands then he would likely have chambering issues.

With this not happening with the other upper the converion could be suspect. Maybe not venting pressure quite as quickly as a GI system causing a pressure spike.
You get a quicker gas impulse with a 16 than you do a 20.

Have you checked the headspace? The chamber could be a smidge short.
Have you checked the firing pin protrusion? .028 minimum .036 maximum.

Let us know-I am curious what you find out as I know damn little about re-loading.

To the OP. I never crimp my AR rounds. My brother never crimps his AR rounds. My grandfather, who has been reloading 223 since well before I was born, has never crimped his AR rounds. None of us have had any problems with that. About half the guys reloading 223 crimp, half don't. A lot of people think there will be setback when the round hits the feed ramps in an auto loader. I've gauged dozens of rounds to see if I have had any setback and I haven't.

26 grains of Varget is at max or less than half a grain below max in all of my books. You are loading way too hot for your first rounds through a new rifle. Every rifle is different, you can't expect what works in one to work in another. You ALWAYS need to build your loads up.

[coop68]

To the OP. I never crimp my AR rounds. My brother never crimps his AR rounds. My grandfather, who has been reloading 223 since well before I was born, has never crimped his AR rounds. None of us have had any problems with that. About half the guys reloading 223 crimp, half don't. A lot of people think there will be setback when the round hits the feed ramps in an auto loader. I've gauged dozens of rounds to see if I have had any setback and I haven't.

26 grains of Varget is at max or less than half a grain below max in all of my books. You are loading way too hot for your first rounds through a new rifle. Every rifle is different, you can't expect what works in one to work in another. You ALWAYS need to build your loads up.

i agree with the above statement! i shoot high-power competitions and i never crimp my rounds there is no reason if you re-size them properly and seat them to your necessary length.

With the load you mentioned it is way to hot if its piercing primers if i was you check your firing pin as it could have a nice creator or moon shape on the tip. if so i would suggest replacing it as it in some cases causes more pierced primers due to being deformed just my experience! another thing invest in a good chronograph it can help set up loads correctly. the books are great for a starting point but that's about it. i would go with the FPS not the grain weight as the amount of powder you put in the case can vary from keg to keg of powder not every batch is the same!

[jmg8550]

May be kinda off the wall but, are you trimming your brass or atleast checking length after resizing? This too could cause a pressure spike. Maximum case lenth is 1.760 inches.

[MattR]

Finally got around to messing with this again, after spending all the money to build it and it didn't work right it found its way into the safe to think about what it had done. But it turns out that I had a mis-sized firing pin hole in the bolt face, replaced the bolt and...BANG...problem solved.