Pierced primers

[PNWFarmer]

Hello all, I had a "cheap" AR 10 in 6.5 CM put together that pierced a primer on one of the first 4 rounds I put through it with Hornady whitetail ammo and wouldn't cycle the next round, I had to manually rack each.. The rifle was put together a couple years ago but I just got around to putting glass on it and try it out. I've read all the possible causes from a FP that's a hair long to headspace issues and the like. I don't plan to shoot it any more until all those are eliminated but I thought I'd get a head start on another possible cause and temp solution to get going if all others check out. When I was putting the parts together for the build I just ordered the standard 308 BCG not knowing the better choice would of been a JP HP bolt kit. Now that I know what I should of done I can't find a JP setup anywhere. This leads me to my ultimate question, I'm wondering if I reload for this rifle can I use CCI #34 primers as a bandaid until I find a JP setup or if those primers are tough enough to withstand the 308 FP.

As far as the cycling goes, after pulling the bolt out it had a gun "grease", not oil so I cleaned all that up and am hoping that's the cycling issue. If it doesn't I know there's alot of alternatives for remedying cycling problems. There's also a lip on the feed ramps that I thought seemed strange instead of being smooth right to the edge of the barrel shank but I've never seen another semi auto 6.5 to compare. TIA.

 

[Twdmar]

Ar10s can take a bit to tune. The extractor spring may be very heavy and so if there is any drag from the magazine or anything else slowing the bolt down, the extractor may not slip over the case rim. Also, a rifle length buffer with may make it feed better and consider an adjustable has block.
I have never used cci 34 primers so I can not speak to that but if you're gonna handhold, try loading down a bit. Also, the ar10s perform better with lighter bullets in the creedmoor from what I understand. The jp bolt is not cheap but probably cheaper than having the bolt bushed and probably a better choice.

 

[PigButtons]

When you say "won't cycle the next round", may I assume that it ejects the spent round fine but doesn't pick up the next one out of the mag? The Creed has about 200 - 400 ft-lbs LESS energy than the 308. If you have a 308 BCG and 308 buffer / buffer spring, you are probably short stroking. Grease vs oil at that level of energy is probably moot.

As for poking a hole in the primer,, you may want to look at the hammer weight and spring torque. Those with the 308 firing pin may be just too much for the primers. You could test this with a spent primer in an empty case and just pull the trigger and see if even without the energy from the inside pushing back if the FP makes a deeper than usual imprint.

 

[PNWFarmer]

Thanks guys. Twd, it does have a rifle length gas tube but not an adjustable gas block, it is something that I'm strongly considering installing. My plan is using it as a 'yote gun so 95-100 grain projectiles mostly.
Pig, your assumption would be correct, fires, ejects but fails to pick up the next round. I'll research some of the weights and see if there's a difference between the calibers. Thanks again.

 

[Twdmar]

Thanks guys. Twd, it does have a rifle length gas tube but not an adjustable gas block, it is something that I'm strongly considering installing. My plan is using it as a 'yote gun so 95-100 grain projectiles mostly.
Pig, your assumption would be correct, fires, ejects but fails to pick up the next round. I'll research some of the weights and see if there's a difference between the calibers. Thanks again.

What magazines are you using? Between the pressure from the spring and drag from the feed ok lips of some metal magazines, you can have feeding issues. Will it lock back on an empty magazine? Will it strip a round out of the mag.if the bolt is released from the bolt stop or does it need to be sling shot?
What length gas tube? IMO, the rifle length or longer is much better. On 308 dpms barrels, the gas port seems often too big, not sure on a creed. Cycling is more a condition of gas pressure than energy differences between the 308 and 6.5.
The mass of the of the firing pin may be an issue, the jp high pressure bolt uses a lighter smaller diameter pin. A good guess would be higher pressure ammunition with a sloppy firing pin to bolt fit allowing too much primer flow.
Do the case rims look like they are being beat to hell? This can give a hint about the gas system.

 

[243winxb]

feed ramps

Many photos here- https://www.thehighroad.org/index.php?threads/show-me-your-308-ar-feed-ramps.815851/

High pressure can cause hard extraction, slowing the bolt. Pierced primers can be high pressure also.
An adjustable gas block is needed.

Reloads may change port pressure timing and aid cycling?

 

[457ciSBC]

Hello all, I had a "cheap" AR 10 in 6.5 CM put together that pierced a primer on one of the first 4 rounds I put through it with Hornady whitetail ammo and wouldn't cycle the next round, I had to manually rack each.. The rifle was put together a couple years ago but I just got around to putting glass on it and try it out. I've read all the possible causes from a FP that's a hair long to headspace issues and the like. I don't plan to shoot it any more until all those are eliminated but I thought I'd get a head start on another possible cause and temp solution to get going if all others check out. When I was putting the parts together for the build I just ordered the standard 308 BCG not knowing the better choice would of been a JP HP bolt kit. Now that I know what I should of done I can't find a JP setup anywhere. This leads me to my ultimate question, I'm wondering if I reload for this rifle can I use CCI #34 primers as a bandaid until I find a JP setup or if those primers are tough enough to withstand the 308 FP.

As far as the cycling goes, after pulling the bolt out it had a gun "grease", not oil so I cleaned all that up and am hoping that's the cycling issue. If it doesn't I know there's alot of alternatives for remedying cycling problems. There's also a lip on the feed ramps that I thought seemed strange instead of being smooth right to the edge of the barrel shank but I've never seen another semi auto 6.5 to compare. TIA.

You don’t necessarily need a JP bolt kit for a successful AR308 build. I think you have multiple issues here, I would chase the cycling issue first.
1. Buttstock configuration- Rifle or carbine?
2. What buffer and buffer spring did you use?
3. What magazines are you using?
4. What brand of bolt?

 

[David Milisock]

Hello all, I had a "cheap" AR 10 in 6.5 CM put together that pierced a primer on one of the first 4 rounds I put through it with Hornady whitetail ammo and wouldn't cycle the next round, I had to manually rack each.. The rifle was put together a couple years ago but I just got around to putting glass on it and try it out. I've read all the possible causes from a FP that's a hair long to headspace issues and the like. I don't plan to shoot it any more until all those are eliminated but I thought I'd get a head start on another possible cause and temp solution to get going if all others check out. When I was putting the parts together for the build I just ordered the standard 308 BCG not knowing the better choice would of been a JP HP bolt kit. Now that I know what I should of done I can't find a JP setup anywhere. This leads me to my ultimate question, I'm wondering if I reload for this rifle can I use CCI #34 primers as a bandaid until I find a JP setup or if those primers are tough enough to withstand the 308 FP.

As far as the cycling goes, after pulling the bolt out it had a gun "grease", not oil so I cleaned all that up and am hoping that's the cycling issue. If it doesn't I know there's alot of alternatives for remedying cycling problems. There's also a lip on the feed ramps that I thought seemed strange instead of being smooth right to the edge of the barrel shank but I've never seen another semi auto 6.5 to compare. TIA.

Pierced primer says high pressure to me. High pressures that don't cycle says possibly a wrong pressure curve to me, an adjustable gas block most likely will not fix an improper pressure curve.

All I can say about a cheap AR is good luck.

 

[10XSHOOTER]

Adjustable gas block my not help if short stroking. you may need to open gas port in barrel.
Pull firing pin and inspect closely. may have a jagged tip.

 

[Cemetery21]

On a brand new build, it helps to cycle the bolt several times (like 25+). That lets the bolt lugs lap into the barrel extension. Otherwise, it's not uncommon to shortstroke on some of the first 10 rounds or so. Lube well also.
That may not be your issue, but it happens. I like adjustable gas blocks on everything. That way I can tune the gas for my load.
Piercing on factory loads could be hard to track down. Some good suggestions above. I think I read that member Carlsbad can bush an AR bolt, if it comes down to that.

 

[skeeljc]

Pierced primers in an AR can often be eliminated with just changing the firing pin.

 

[NZ_Fclass]

Back when our Socialist dictators allowed AR's, I had a similar problem with a new build. - Cycling that is. I cured it by moving the gas key on the bolt. An 1/8 of an inch can make a difference. And yes - measure your firing pin protrusion.

 

[jelenko]

Back when our Socialist dictators allowed AR's, I had a similar problem with a new build. - Cycling that is. I cured it by moving the gas key on the bolt. An 1/8 of an inch can make a difference. And yes - measure your firing pin protrusion.

You moved the gas key on the bolt carrier? I assume you moved it back towards the butt? What effect does that have

 

[NZ_Fclass]

You moved the gas key on the bolt carrier? I assume you moved it back towards the butt? What effect does that have

Actually moved it forward. It was not a factory staked part and had been assembled ( by me) too far to the rear. I guess it improved the "seal". Whatever the cause - it cured the cycling issue. I had tried all the other bits - gas block, buffer spring etc.

 

[PigButtons]

Actually moved it forward. It was not a factory staked part and had been assembled ( by me) too far to the rear. I guess it improved the "seal". Whatever the cause - it cured the cycling issue. I had tried all the other bits - gas block, buffer spring etc.

Makes good sense to me, mass production tolerance stacking over multiple vendors can have you chasing your tail for sure. Good tip here. Sorry about your sorry state in NZ. I hope sanity returns but once freedom is lost it is hard to restore.

 

[PigButtons]

One other thing to look at on your build: is the port in the gas block perfectly aligned with the port in the barrel. More than one builder has had extraction problems due to mis-aligned gas blocks.

 

[NZ_Fclass]

Sorry about your sorry state in NZ. I hope sanity returns but once freedom is lost it is hard to restore.

You are quite right.
You know, it wasn't the fact that it was semi-auto's that got banned, along with pump action centrefrires etc - it was the lies and spin that these awful people used. " Concerns that gun clubs were racist" was a cracker. "It will make New Zealand safer" ( didn't) and the very thought that my adopted country which I love has allowed this happen. And why me? I have no convictions, not racist, except to Indian phone scammers. Married for 40 odd years. I have an ISSF judges licence, National range office quals for pistol, ex NZ team manager and have always been a competitive shooter. And at 70 years old, past being a terrorist or bank robber. But let's not go down the conspiracy rabbit hole - but there's truth out there somewhere...

 

[Twdmar]

Makes good sense to me, mass production tolerance stacking over multiple vendors can have you chasing your tail for sure. Good tip here. Sorry about your sorry state in NZ. I hope sanity returns but once freedom is lost it is hard to restore.

The stacking of out of spec parts is a problem with the ar10 that does not really exist with ar15s, a more refined design.
An aero 308 bolt carrier I have had the cam pin that rubbed on the bottom of the gas key..
Make sure the bolt by itself goes into battery. Make sure the bolt does not bind on the carrier. Also, the original psa lowers were out of spec and with a 2 stage trigger the bolt carrier binds on the hammer.

 

[SweaterDood]

We’re the primers Small or Large in size? I have never experienced the issue, personally, but do hear that a “regular” diameter firing pin (.086”) can cause issues with SRPs. I assume that most all factory 6.5 CM loadings use LRPs, though.

That said I have a friend with an Impact 737 bolt action on a match rifle that has been piercing primers lately. Difficult to nail down with component shortages, for sure. Already checked firing pin protrusion, pin head for rough/sharp edges, etc. basically down to swapping a bolt/firing pin or bad lot of primers.

 

[Rsadams]

One other thing to look at on your build: is the port in the gas block perfectly aligned with the port in the barrel. More than one builder has had extraction problems due to mis-aligned gas blocks.

+1 on this , seen it many times...