?perforated? primers

[pastorpaul]

i need the help, understanding and expertise of the forum members on this for a very good friend of mine in southern indiana. he called me today about an issue that arose from him shooting his ar-15 earlier today. he had a standard gas operated m4gery and never experienced this problem previously. he sent it off to get a gas-piston modification done to it. all that was done was exchange the gas block, drop in the gas piston assembly and modify the bolt to accept the new assembly (at least that is all i recall him saying they did). when he got it back from the ones who did the work he went out to shoot it. he was shooting some recently purchased military surplus ammo, LC stamped. he shot 30 rounds. the 30th round failed to eject completely. upon inspection he found 5 out of the 30 casings had punctures into the primer body and the one that hung up on him had the primer completely removed from the case. he later found it rattling in the magazine. it, too, was punctured. he says all the other cases had what he would call normal indents from the firing pin. he stated there was no evidence of excessive pressure from the primer being flattened or shown on the cases.
he asked if i could explain this phenomena. the best i could share was it sounded like "soft" primers but one would think all or at least most of them would be punctured. i told him i would ask on the mnguntalk site because i believe their are several more experienced and knowledgeable individuals here than i, so...
what do you think is going on? is this a simple "bad" ammo problem? has something changed in his ar since he had the gas-piston added? other??
i told him i would send him the web address and he could follow up for himself.
your help will be appreciated by him and i.

[farmerj]

I have seen this one other time.

On an M1 Garand.

First thing that comes to mind is to check the firing pin protrusion. Too much and you would end up with a pierced primer.

That is my first gut instinct.

[Pinnacle]

Adding a piston assembly would not change anything with the firing pin as a part - first I would look at the ammunition.

Then I would look at the firing pin - protrusion as FarmerJ said would be a suspect - the other would be a burr on thepin that may have been cuased by dropping it point down during re-assembly.

Stumped until those variables are eliminated

BUT

There is one thing - with a piston there is a lot more retained gas in the system - I wonder who did the work and what the make of conversion is on the gun. Fins that out for me and PM

I have been tinkering with a piston coversion that will be available soon - we were having some pressure issues when we did nto tap the gas off fast enough - like 1/2" from the top of the port -

Sometimes a poorly designed piston system can tear a gun apart piece by piece.

[Ramoel]

The last time I had a gun pierce primers it was a tiny chip out of the firing pin tip. It was hard to see without a magnifying glass. I stoned it round again and it has worked great ever since.

[farmerj]

The last time I had a gun pierce primers it was a tiny chip out of the firing pin tip. It was hard to see without a magnifying glass. I stoned it round again and it has worked great ever since.

You mention this and I now remember and have confirmed that yes, there was a chip out of the firing pin on the M1. I don't remember him having ever fixed it or having heard what was done to fix it. That was some 6 years ago.

I am guessing since he was able to confirm so quickly, the rifle would still have a chipped firing pin. We originally thought it was a result of the primers being pierced that caused the chip, maybe it's really the other way around.

[Rip Van Winkle]

There are only 2 reasons I know of that will cause pierced primers.

1) the most common, Over pressure loads.
2) A misshapen firing pin tip.

As your friend had a blown primer on one of his loads I'd say #1 is the problem. My guess, and thats all it is, is that either he's shooting different ammo than he's claiming or he has a very short throated commercial .223 chamber which isn't compatible with military surplus 5.56mm ammo.

Of the people I know* who've pierced primers on their AR's, most have had to replace both their firing pins and bolts. Once primers start to pierce, the cutting action of the escaping gasses start reshaping the firing pin tip and bolt face.

If he were my friend, I'd advise him to take his rifle with the offending brass to a reputable AR gunsmith for an inspection.

*note: Most of the folks I know are competitive shooters pushing the upper limits of safety.

[farmerj]

There are only 2 reasons I know of that will cause pierced primers.

1) the most common, Over pressure loads.
2) A misshapen firing pin tip.

As your friend had a blown primer on one of his loads I'd say #1 is the problem. My guess, and thats all it is, is that either he's shooting different ammo than he's claiming or he has a very short throated commercial .223 chamber which isn't compatible with military surplus 5.56mm ammo.

Of the people I know* who've pierced primers on their AR's, most have had to replace both their firing pins and bolts. Once primers start to pierce, the cutting action of the escaping gasses start reshaping the firing pin tip and bolt face.

If he were my friend, I'd advise him to take his rifle with the offending brass to a reputable AR gunsmith for an inspection.

*note: Most of the folks I know are competitive shooters pushing the upper limits of safety.

And that is why the Mosin's have a specific tool for setting firing pin protrusion. Not many even look at it any more.

[farmerj]

There are only 2 reasons I know of that will cause pierced primers.

1) the most common, Over pressure loads.
2) A misshapen firing pin tip.

As your friend had a blown primer on one of his loads I'd say #1 is the problem. My guess, and thats all it is, is that either he's shooting different ammo than he's claiming or he has a very short throated commercial .223 chamber which isn't compatible with military surplus 5.56mm ammo.

Of the people I know* who've pierced primers on their AR's, most have had to replace both their firing pins and bolts. Once primers start to pierce, the cutting action of the escaping gasses start reshaping the firing pin tip and bolt face.

If he were my friend, I'd advise him to take his rifle with the offending brass to a reputable AR gunsmith for an inspection.

*note: Most of the folks I know are competitive shooters pushing the upper limits of safety.

And that is why the Mosin's have a specific tool for setting firing pin protrusion. Not many even look at it any more.

[DeanC]

That picture is so huge it makes it hard to read the thread. And I have my resolution set at 1280x1024 on a 20" monitor.

[farmerj]

That picture is so huge it makes it hard to read the thread. And I have my resolution set at 1280x1024 on a 20" monitor.

edited for the CORRECT one that should have been there.

[pastorpaul]

i truly appreciate everyone's responses and pm s. i called my friend after work today and he gave me some more info. i asked him to sign up to mgt and share first hand his experience as well as read your responses. i think it is actually going to be an ammo issue and a possible firing pin issue. both of us think he did not get actual military ammo but was deceived into thinking it was when in actuality it was reloads of some LC brass. i'll let him explain and share for himself. thanx

[bear247]

Hey folks this is bear, the primer problem is that the ammo does not have the military crimp on the primer. The primers just fell out of the shell some landing in the mag and the others fell into the trigger area causing a couple of trigger mishaps. As for the new piston system, it was installed by primary weapons systems at http://www.primaryweapons.com. I also had thier compensator fs556 installed because it was designed for use with the halo suppressor that i own. The piston system works great, it has a switch that you can change for use with or without the can. PWS does bore the gas whole .001 for better pressure release. There is another company out there that has a DIY piston system, it is GSR-35 Black lighting by Ares defence. Thanx for all the people that responded to this ?, I really appreciate it. Later...

[farmerj]

IF you suspect the ammo.

Either try it in another rifle, or go and buy some fresh factory ammo.

I doubt it. The M1 we had issues with used the same ammo that never had issues in my personal M1. Partly why I don't think ammo is the first issue to look at.

One "option" is to switch BACK to a gas system to see if it continues. Considering the severity of the situation, it's one of the first things I personally would do. If it doesn't continue, the issue would be in the new piston system.

It would almost seem like a timing issue with how the bolt carrier might not be unlocking the bolt fast enough. or the piston system is not bleeding it off like the gas system was designed.

did they open the gas port enough after the piston system was installed.

Just some additional thoughts.

[bear247]

The more I thought about it today, I remember that before the piston was installed, back in the summer I shot the same ammo and had a few primers fall out after I picked up the ammo from the ground. But I will try some different ammo as soon as the weather breaks, to see if the same thing happens or not. Thanx

[bear247]

Got some diff ammo and had no problems at all...it has to be the mil surp. thanx for your input.