UPDATE: SOLVED PROBLEM    i have tried a different ammo,,  hornady with a lighter bullet and it works exceptionally well now.    doing happy dance.

THANKS FOR ALL THE INFO AND HELP

situation:    hoping this isn't a stupid question.   maybe just the gas block.  

bought a very low round count ar10,  decent components, Criterion 16 inch barrel. JP matched high pressure bolt. JP silent capture springs. Rise Armament Trigger, unknown adjustable gas block,

anyway,, when i got it, i put a 338ba suppressor on it that i wasn't using, and used fgmm 6.5 factory 130 berger hybrid OTM ammo.    i put 10-15 thru it with a trij mk3 and then got squirreled.  it shot great and no probs.     2 years later,  circumstances made me want to revisit it,  but i put on a ultra 7 .30 cal suppressor.      I don't remember dicking around with the gas block last time.   anyway,,   it seemed like a lot more gas than usual went in my face but i didn't remember exactly from 2 years ago so, i shot again and it didn't cycle right.   looking in the mag and found a blown primer.  so i think it clogged up the mag.   i picked up the 3 cases and sure enough a blown primer,  also the primers look a little flat,, and decent marks on head.  

i mean, i have seen flatter primers,  it doesn't look too bad.   but

i know ar's are pretty hard on cases but having a blown primer seems extreme.   my thoughts are maybe the smaller suppressor caused more gas build up,, perhaps i should adjust gas block but it still seems a little weird,  it's just factory federal ammo, how hot can it be?


appreciate any thoughts.   merry christmas to all!

Heavier buffer

I have a 6.5 Creedmoor that has run flawless. Standard bolt and JP SCS configured H with and SLR adjustable gas block. It shoots factory and hand loads with no issues and is really easy on the brass. It is an Aero upper, Rainier Ultramatch barrel and rifle length gas.

Had a 6mm Creedmoor that would pierce primers constantly. HP bolt and JP SCS configured H with and SLR adjustable gas block. Even with an HP bolt it would pierce primers quick and broke a titanium firing pin. Primers were pierced or blown no matter the the ammo, factory or hand loads. Hand loads even with charges on the low end of the tables would still be the same. Primer pockets suffered and lost a lot of brass as a result.  It was an Aero upper, Wilson Combat barrel and rifle length gas. Again this was with any ammo suppressed or not. Very aggravating

Got tired of messing with the 6mm Creedmoor setup and switched barrels to a 6.5 Creedmoor Proof Carbon +2 gas length barrel. Used a new HP bolt and JP SCS configured H with and SLR adjustable gas block. It started piercing primers too. Messed with the gas, no real effect. Configured buffer as H2 and not much there either. Took the SCS and added a heavy spring (forget which color it is) to the H2 setup with a quick gas adjustment afterward. Now that rifle runs 100% and never pierces anything with or without a can. Brass is in good shape and primer pockets are excellent. All the changes slowed the bolt and that is where I believe the problem was.

My gas adjustments are to get the rifles cycling without a can and that's it. Once set they are left there. I can then place any of my cans on them and they run just fine.

I need to take the 6mm Creedmoor and get an upper and mess with it some more. I now have 2 6.5 Creedmoor rifles, but want the 6mm bacl. With the AR10 it is more of a balancing act with different cartridges. The first 6.5 mentioned, gas adjustment and done. The second was a lot more adjustment and experimentation to get it dialed in even after a caliber change similar to what worked on the first.

Ran into this very thing years ago with my build.  Headspace isn't your problem.  Kreiger/Criterion recommend JP bolts because they are dimensionally consistent.  Its on their website and I called them about my kreiger barrel when I had this same issue.

#1 Federal brass is relatively soft.  For whatever reason, the fgmm 130gr primer pockets don't last.  I had so many culls due to big primer pockets I just started throwing brass away...literally no way to reload it after one firing.

#2 You increased backpressure when you suppressed the rifle.  More gas increases bolt unlocking speed so your bolt is unlocking a bit earlier than it was.  This allows the primer to back out of the pocket.

#3 You can address this by reducing gas via AGB and/or increase buffer weight.  I was using a gen1 UBR so my fix required a heavier spring as well (limited to carbine-length buffer).


In the end, I started reloading the 130 otm in Hornady brass.  Eventually I ditched the projectile because I had better long range results from the 140 hybrid target, 142smk, and 147eldm.

This. Need to go with a heavy buffer.

thanks, good info.   i actually just checked, it is a 16" criterion barrel, not a 20.    so i am probably at typical rifle length,  do you think heavier buffer would help as someone stated above?

thanks!   excellent info.   i wound up with the federal 130 because, 1) i didn't want to reload for this rifle,  and 2)  I already had a case of the ammo which was sitting around unused   and 3)  140 was overkill for the intended purposes plus i was hoping for a tiny bit of less recoil with a 130

What buffer weight?

Both my 6.5 guns have 8oz buffers and adjustable gas blocks. You want the bolt to stay closed as long as possible, especially with a suppressor on it.

it has a jp silent capture spring set up,, will check weights.  

thanks!

apparently, i already have the heaviest buffer weight for the silent capture spring,  hmmmm.

I had to use a Slash heavy carbine buffer in addition to adjusting gas and a Tubbs flatwire spring.  So, don't know if my solution is relevant in your case.


I'd try tuning the gas block before dumping your buffer setup.

apparently, i already have the heaviest buffer weight for the silent capture spring,  hmmmm.

I had the same problem with mine.. to the point where it would blow the primers out and lock the gun up.
Sent it back to Savage when I discovered that it only did it with 147EDLMs and they determined it was my chamber being to short.. the 147s were jamming into the lands and causing pressure spikes.

Yeah, the fgmm berger 130s are loaded mag length and the ogive is further back on the projectile.

I'd bet you would've had issues with the 142gr SMKs too if you tried them.

Likely, It took me a long time to figure out that's what was happening since I mainly shoot my reloads and the load is admittedly hot.
But that recipe has been shot in dozens of rifles with nothing more than light ejector marks.
I tried the factory loading and it did the same thing.

but if the ogive is further back, then wouldn't it not be likely to be jammed into lands?

i am not arguing about my ammo,, 130gr berger fgmm,  it is defintely pretty hot for my gun

i mean, 130 gr is not a big 6.5 bullet by any means

so what did you wind up doing?   were you loading your own ammo?

so what did you wind up doing?   were you loading your own ammo?

I prefer to roll my own long range/precision rounds.
Savage replaced the barrel in it.

ETA: how I knew it wasn't my ammo was testing factory Hornady 147gr.
same projectile but not loaded as hot.. got the same results so it couldn't be my load.
I already had the rifles gas tuned to as low as it would go and still lock back so it wasn't over gassed.

You're correct, I misspoke.  Ogive closer to tip than base.  142smks are almost "bulbous" compared to the hybrid target projectile.

You'll know quick if you're in the lands.  You can use dykem or candle smoke. Chamber a round, eject it, check for marks.

i've done that with a permanent black marker before as well.  

anyway,    i have tried a different ammo,,  hornady with a lighter bullet and it works exceptionally well now.    doing happy dance.

Good!

I think 6.5 federal brass is soft garbage and that's a big part of the problem.  Even if you didn't blow primers, I'd bet the primer pocket is too loose to reload.