6.5cm blown primer factory ammo AR10 platform question

[243winxb]

it is advisable to reduce the amount of gas flowing through the system by closing the gas port until the gun operates correctly.

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

 

[Coyotefurharvester]

Superlative arms has a block with a bleeder, probably needed with the suppressor. Hornady pretty much covered it.

 

[Webster]

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!
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Bolt actions are much friendlier.

 

[natdscott]

I SERIOUSLY Doubt that,.. it's an Ammo problem !
Usually, every Lot of Ammo IS, Tested at Factory, before, shipping.
Have a Friend, shoot a couple, in a Good, Bolt action First, before complaining to, Factory.
Probably have,.. a "Can" Pressure, Issue !

You don't remember the Federal XM193 issues, then?

 

[rockwind1]

The issue is likely the suppressor rapidly fouling the barrel. I experienced this getting ready for a suppressor match earlier this year.

Clean the barrel and shoot it without the can. I expect the ejector swipes may go away. Federal primers are on the softer side. The case on the left in your picture is about what I would expect from normal Federal factory ammo. If this resolves the problem, then that ammo is likely not going to be compatible with that can.

how fast can a supressor foul the barrel?

 

[Idaho-Lefty]

You don't remember the Federal XM193 issues, then?

Nope,.. I've shot them ( NO Problems ) and still have, a couple of boxes left, around here, somewhere.
Tell me more, was there,. a "Re-call" on them ??
Once in a while, the Factories DO,.. "Miss something" !
See Posts 21 and 22 and the message from,.. Hornady about, 6.5 Creed Ammo and SuperPerformance Powder

 

[Coyotefurharvester]

The barrel will foul faster with a suppressor, than without. More powder(case capacity) more fouling. Run dirty powders, more fouling.

 

[ZenArchery]

I’d buy second brand of different ammo and see how it performs. As one who test loads to extreme pressures. That has all the looks of ammo issue in an AR10.
Have you tried chambering one and then ejecting it? If it’s Uber difficult to run the charge handle then the bullet is jamming into the lands.

 

[rr1220]

Not sure this applies but a few years back when I bought my savage evolution in 6 creedmoor before firing I measured the factory ammo BTO and found with the factory chamber the out of box ammo would be jamming the bullets and sure enough the couple of rounds fired were over pressure and also popped some primers
I reseated the bullets a little deeper and stopped popping primers though there were still pressure indicators

 

[William Vogel]

so, further research has me leaning towards increasing buffer weight and adjusting gas block, will also put my 338 supressor back on.

It shouldn’t have anything to do with the suppressor or the gas block. Everything happening to the brass is before the bullet exits the barrel. I would look at the barrel/bolt lock up for headspace (which is probably not the problem), check that apon chambering a round that the cartridge freely can be removed and that the bullet isn’t pushed back into the case. The barrel seems to be too “tight”. I’m expecting that the barrel isn’t excessively long, it’s an AR with a suppressor. Also remember that perfectly good working stuff isn’t sold for the most part and never take a seller’s opinion as to why they no longer need what they are selling. Perfectly good stuff is kept. This issue is good reason for selling. Just for the hell of it, shoot it without the suppressor for 50 rounds or whenever it keeps leaving ejector marks. The ejector marks/case head flow are enough sign of excessive pressure. I’d pull some bullets, chronograph velocity, measure powder charge etc, etc, etc. I’d be skeptical of firing it again until some proof is found.

 

[markm87]

The best luck we've had with the AR-10 in 6.5cm was when we removed the suppressor and dropped the handload a full grain.

Not that the can is causing the initial spike in pressure, but suppressors just make semi auto gas guns awful to shoot.

Dropping the load, made the gun much more shootable and reliable, with little impact on the long range "come ups". My buddy (who owns the gun) said "Man! I could shoot that all day now"

 

[rmeyerwy]

Couple of things I notice in the picture, 1) the lack of cratering around the firepin and the flatness isnt that bad imho on the 1st 2, some but eh.. 2) Maybe I just cant see if from the angle but the left 1 doesnt seem to have an ejector imprint like 2 and 3, the left one may not be too bad overall, but you notice the color change from left to middle to right? a lot of difference, like there is a buildup of something causing more fouling as the shots progress...

 

[rockwind1]

Couple of things I notice in the picture, 1) the lack of cratering around the firepin and the flatness isnt that bad imho on the 1st 2, some but eh.. 2) Maybe I just cant see if from the angle but the left 1 doesnt seem to have an ejector imprint like 2 and 3, the left one may not be too bad overall, but you notice the color change from left to middle to right? a lot of difference, like there is a buildup of something causing more fouling as the shots progress...

i also thought the lack of cratering made it not as bad as it appears. but anyway,

UPDATE: SOLVED PROBLEM i have tried a different factory ammo,, hornady with a lighter bullet and it works exceptionally well now. PRIMERS STILL A LITTLE FLAT, VERY FAINT EJECTOR MARKS or none. shot 20 rds of new ammo and adjusted gas block a little bit. shoots really, really nice now. out to 400 with a trij mk3 with ease! NO EXTRACTOR MARKS. doing happy dance.

 

[rockwind1]

I’d buy second brand of different ammo and see how it performs. As one who test loads to extreme pressures. That has all the looks of ammo issue in an AR10.
Have you tried chambering one and then ejecting it? If it’s Uber difficult to run the charge handle then the bullet is jamming into the lands.

you Sir, would be correct and are awarded 1 million bonus points! i tried some hornady and got lucky, seems to shoot great now.

 

[rockwind1]

Couple of things I notice in the picture, 1) the lack of cratering around the firepin and the flatness isnt that bad imho on the 1st 2, some but eh.. 2) Maybe I just cant see if from the angle but the left 1 doesnt seem to have an ejector imprint like 2 and 3, the left one may not be too bad overall, but you notice the color change from left to middle to right? a lot of difference, like there is a buildup of something causing more fouling as the shots progress...

the left one does have the same marks, it is just the light playing tricks, same with the buildup. i think they were just deeper in the mag and subjected to more blowback.

 

[whatsupdoc]

The ammo most likely is not the issue, switching to different ammo may show
better results probably due to it being loaded to a lower pressure or the
pressure curve is shorter than that ammo you are having issues with.

In my opinion and experience I would never use a 6.5 creed barrel on a large frame AR without a +2 gas system. An adjustable gas block will not help.

 

[Rocketvapor]

OP has a 16" barrel.
A suppressed 6.5CM with a short barrel.

@rockwind1
Glad you found a round your gun likes.

 

[rockwind1]

The ammo most likely is not the issue, switching to different ammo may show
better results probably due to it being loaded to a lower pressure or the
pressure curve is shorter than that ammo you are having issues with.

In my opinion and experience I would never use a 6.5 creed barrel on a large frame AR without a +2 gas system. An adjustable gas block will not help.

i agree, however, this is an awesome gun for the price i paid, and the 16" barrel serves a specific purpose for what i wanted. i wonder if they make 16" barrels with +2 port? i've never measure to see if it would fit, would look kind of weird but,,,

 

[markm87]

Aside from the Ammo issue, if the suppresser must be used, Black River Tactical makes gas tubes that reduce the gas at the port to help get the bolt speed reasonable. This is MUCH better than socking an over-weight buffer in the gun.

We run these in AR-15s and AR-10s. It's a great way to correct over gassed ARs, can or no can.

 

[ToddKS]

how fast can a supressor foul the barrel?

In my case, less than 30 rounds with the powder in question before extremely heavy bolt lift was encountered. Switching powder solved the issue.