One in a million AR15 issue

ny32182 · Oct 27, 2019

So I was out shooting my BCM midlength for the first time in a while today. All was going well until I put the suppressor on. Within 10 rounds, it had failed to go into battery all the way. I looked in the action, didn't see anything obvious. Ran the charging handle once, same issue. Ran it again it again and it went all the way into battery and then was a single shot straight pull bolt action, seems to be getting no gas at all.

Looking at some of the brass fired with the suppressor, some of the primers were blown out. This is British surplus Radway Green that I've had in the closet for years. Everything fired without the suppressor looked normal and has in other rifles, EXCEPT, I think this happened once before with this ammo (without the suppressor)

Packed it in and went home. Looking at the gas tube, seems to be in the right spot. Looking into the carrier key, and compared to another one, it appears to me that one of the primers got stuffed into to the gas key. I can't imagine the odds of this happening; it must be pretty amazing. Shining a light in there, it just appears to be closed off in a shorter distance than others from other rifles. What I can see appears to be the size and shape of a primer cup expanded to fill the gas key.

So, if this is the issue, what happens... carrier key replacement? Can I get the new key staked properly? What is the torque spec on the two bolts? Any other tips? Will have to google around on this one for a bit.... can't imagine the odds of this, but also can't imagine what other possibility there is at this point. I've compared the gas tube position to other functional guns and it looks to me like it hasn't moved. Thoughts welcome.

.455_Hunter · Oct 27, 2019

You are not the first- I have heared of this before. I would try a drill bit first before replacing the key.

Skylerbone · Oct 27, 2019

Gas keys are cheap as are screws and sealant. If need be.

Varminterror · Oct 28, 2019

Compressed air through the carrier port. Rubber nozzle tip on one port, thumb covering the other. Usually doesn’t take much to pop them out.

G.barnes · Oct 28, 2019

Make sure there is no damage to the bolt. Saw a guy with an M&P sport that had some primers blowing out. On got stuck in the bolt lugs I guess cause he was doing fun be then it turned to a single shot. Even manually operating it you could feel it bind. Had a spot on the side bolt by the lug where it had a big gouge in it.

Walkalong · Oct 28, 2019

Had it happen to me, definently not the first thing you look for.

243winxb · Oct 28, 2019

Hornady- Back pressure from suppressors.

https://www.hornady.com/support/superformance-in-gas-operated-firearms

If the firearm and the ammunition are not in sync, there can be what is commonly identified as “pressure signs” on the cartridge case. This is exhibited by the movement/marring of the head of the cartridge case, cratered primers, flat primers, ripped or ruptured cartridge cases, “popped primers”, and/or any combination of these effects. If any of these “pressure signs” are apparent, stop firing immediately. If an adjustable gas system is installed, it is advisable to reduce the amount of gas flowing through the system by closing the gas port until the gun operates correctly.

The powder used in some factory ammo, may not work well with a suppressor?
I seen one 5.56 where soot was all the way back to the case head after just a few rounds.

entropy · Oct 28, 2019

Try Varminterror's tip first, Skylerbone's second, if blowing it out doesn't work. When I was an Armorer, we just replaced the key, but blowing it out sounds a lot easier to me.
There aren't too many issues with an AR I haven't seen; while this is one of the less common, it does happen.
BTW, adjustable gas blocks can be handy on an AR with a can. Not necessary, just handy.

taliv · Oct 28, 2019

the late great pat rogers used to have a brief section in his carbine class discussing this malfunction. also one that's slightly more annoying to fix, which is when the primer falls into the cam pin hole in the carrier. in this latter case, key is to recognize it quickly, because some of the remedial action drills will crush the primer in there and make it nearly impossible to extract. once recognized, you have to invert the rifle and shake it to get the primer to fall into the charging handle.

milemaker13 · Oct 28, 2019

I guess this is the reason for crimped primers on military ammo?

climbnjump · Oct 28, 2019

243winxb said:
The powder used in some factory ammo, may not work well with a suppressor?
I seen one 5.56 where soot was all the way back to the case head after just a few rounds.

Um, yep. I've seen that on my AR when running a suppressor and factory ammo. My hand loads can be tailored, of course, and run fine.

bfoosh006 · Oct 28, 2019

Good thinking on the blow it out aspect. I can't say that would have crossed my mind.

And I "thought" the British surplus Radway Green ( 62gr ? ) was under powered, for the Brit's Bullpup Rifle the SA80.

You might consider breaking down a few rounds , looking for powder deterioration.

A long shot, but worth the time.

Walkalong · Oct 28, 2019

Walkalong said:
Had it happen to me, definitely not the first thing you look for.

DustyGmt · Oct 28, 2019

Wow. Doesnt sound possible. Lol.

climbnjump · Oct 29, 2019

DustyGmt said:
Wow. Doesnt sound possible. Lol.

Oh, sure it does... Kinda like dropped toast always lands buttered side down!

Nature Boy · Oct 29, 2019

That’s incredible

taliv · Oct 29, 2019

i don't really know but i suspect that sometimes there could be a substantial air flow moving into the key that kind of sucks the primer in

ponchh · Oct 29, 2019

If it won't blow out, my next step would be to drill a hole in the primer and screw an extractor into it. Then hopefully pullout out. But if you don't have the tools on hand, they would probably be the price of a new key.

ny32182 · Oct 29, 2019

Well I was able to drill a small hole in it and then drag the remaining ring out with a small allen wrench. I think I got all the shards out but will function check it at the range asap, maybe with just a couple rounds to make sure anything left gets blown into the carrier where I can clean it out.

Mine was same as Walkalong's picture but the other way around with the inner part of the cup visible, but darkened with fouling. It wasn't shaved or anything. Absolute full diameter primer right in the key. I wish my Dillon was that accurate at placing primers all the time. I'm amazed this is actually a thing.

Thanks all for the input.

ny32182 · Oct 29, 2019

G.barnes said:
Make sure there is no damage to the bolt. Saw a guy with an M&P sport that had some primers blowing out. On got stuck in the bolt lugs I guess cause he was doing fun be then it turned to a single shot. Even manually operating it you could feel it bind. Had a spot on the side bolt by the lug where it had a big gouge in it.

Bolt looks fine... I did check that; thanks.

I guess this is the reason for crimped primers on military ammo?

This is crimped military ammo... they came out anyway. Obviously I don't shoot ARs a ton or I would have seen this before, but based on my sample size and the fact I have seen it happen once with this ammo in another unsuppressed rifle, I'm thinking it is mostly fault of the ammo. Fully 50% of the ammo I fired here suppressed semi auto (about 5 out of 10) turned out to have blown out the primers, while I think none of the ~120 unsuppressed rounds did. So clearly it is an issue with the dynamics of the suppressor on this particular rifle and ammo combination.

And I "thought" the British surplus Radway Green ( 62gr ? ) was under powered, for the Brit's Bullpup Rifle the SA80.

It is 62gr, advertised as M855 spec.

ny32182 · Oct 29, 2019

DustyGmt said:
Wow. Doesnt sound possible. Lol.

This is the kind of story I never would have actually believed without seeing it. I'm too skeptical I guess.

ny32182 · Oct 29, 2019

243winxb said:
Hornady- Back pressure from suppressors.

https://www.hornady.com/support/superformance-in-gas-operated-firearms

The powder used in some factory ammo, may not work well with a suppressor?
I seen one 5.56 where soot was all the way back to the case head after just a few rounds.

Maybe one of the ten showed a mildly significant divot from the ejector pin, and a couple showed a visible ring near the case head, and I discarded those. Everything without the suppressor looks fine. No cratered primers in any of it, at least none that still had the primers in them.

This gun currently has a standard (non H) carbine buffer. I don't remember the details but I would not have arrived at that buffer by accident years ago when I got this gun; I always research and use what I think is the right one. I wonder if it should actually have an H, at least with the suppressor.

taliv · Oct 29, 2019

you prob need an H2
if you're blowing primers, something is wrong. you should stop until you figure it out.
just a guess on my part, but i'd put money on your chamber not being properly reamed.

ny32182 · Oct 29, 2019

One other note: I've fired probably 100+ of my handloads with good bullets through this gun suppressed with nary an issue, which is another reason I'm currently thinking it is primarily an ammo problem.

ny32182 · Oct 29, 2019

taliv said:
you prob need an H2
if you're blowing primers, something is wrong. you should stop until you figure it out.
just a guess on my part, but i'd put money on your chamber not being properly reamed.

Could this be safely proven out with different ammo, etc?

One in a million AR15 issue

Member

Member

Member

Member

Member

Moderator

Member

Member

Moderator

Member

Member

Member

Moderator

Member

Member

Member

Moderator

Member

Member

Member

Member

Member

Moderator

Member

Member

Similar threads