Please Help Me Figure Out this Problem

[MistWolf]

I am looking at the photos on my phone and will have to wait till I get home to look at them on a larger screen. However, there does not appear to be more than normal flattening of the primers and I get ejector marks from my shorty upper, even with 223 ammo. Also, high pressure isn't the only thing to cause primers to pop out of the pocket.

In any case, when Cory mics the case webs, we'll know m more. Case web expansion is a more accurate indicator of what's going on

[Jim D]

I've shot a bunch of that ammo from the same lot you have Cory (70gr GMX), no issues in two of my rifles.

Something seems like it must be off between the chamber and bolt... I don't know of any other way to see massive pressure signs like that, particularly across a variety of different ammo.

HOW in the hell it's happening now is totally a mystery to me, though.

[tom12.7]

How would you characterize those attributes? And to what possible causes?

[CoryCop25]

Ideas for Monday's range trip....

Bring a pile of M193 and see how that shoots.
Bring another BCG and shoot some more Hornady GMX.

After Monday...
New rifle spring.
Find Go-no go gauges.
Give some GMX to someone who has a suppressor.

I shot 900 rounds of a mixture of
Freedom Blaster
Hornady Steel Training
Federal 55gr .223 with Sierra Game Kings (PA State Police Load)
BEFORE any problems occurred with this rifle in its current configuration.

[Iraqgunz]

I wouldn't even waste time with the Go/No Go nonsense. Also, if it's not a correct 5.56, not .223 gage, you're spinning wheels.

I would measure that gas port. A nice port size would be about .078. I also agree with Ryno12 as it looks like there is some pressure stuff happening. The one on the far right looks like the primer is almost pierced.

It's entirely possible you have bad ammo. Get some KNOWN ammo from your stash and shoot it. KNOWN ammo means you have shot it before and never had issues.

Ideas for Monday's range trip....

Bring a pile of M193 and see how that shoots.
Bring another BCG and shoot some more Hornady GMX.

After Monday...
New rifle spring.
Find Go-no go gauges.
Give some GMX to someone who has a suppressor.

I shot 900 rounds of a mixture of
Freedom Blaster
Hornady Steel Training
Federal 55gr .223 with Sierra Game Kings (PA State Police Load)
BEFORE any problems occurred with this rifle in its current configuration.

[cemoulton]

Scratch that. Sorry I totally read that wrong or got crossed up on post.... Maybe too much whiskey.

That being said. Or looks like a cross between very high pressure ammo, over gassed barrel and or too tight a chamber or too much head space.

[tom12.7]

I wouldn't even waste time with the Go/No Go nonsense. Also, if it's not a correct 5.56, not .223 gage, you're spinning wheels.

I would measure that gas port. A nice port size would be about .078. I also agree with Ryno12 as it looks like there is some pressure stuff happening. The one on the far right looks like the primer is almost pierced.

It's entirely possible you have bad ammo. Get some KNOWN ammo from your stash and shoot it. KNOWN ammo means you have shot it before and never had issues.

I would generally agree with this, except for the gas port size. A carbine gassed 12.5" AR with a .078" port is aggressively gassed. With the addition of a silencers function in barrel length towards it's function to the action system is a bit much, even with the A5H4 buffer masses and known good springs. I would rather prefer some options in the .065ish" range for this use.

[tarkeg]

Ideas for Monday's range trip....

Bring a pile of M193 and see how that shoots.
Bring another BCG and shoot some more Hornady GMX.

After Monday...
New rifle spring.
Find Go-no go gauges.
Give some GMX to someone who has a suppressor.

I shot 900 rounds of a mixture of
Freedom Blaster
Hornady Steel Training
Federal 55gr .223 with Sierra Game Kings (PA State Police Load)
BEFORE any problems occurred with this rifle in its current configuration.

I know that's a good barrel, but if you have access to either Ned's gauge or reamer I'd use those first. I've had Ned's reamer remove a little material from a DD chamber before.

[Iraqgunz]

That port size is actually COMMON among several respected and known names. In fact, my Kino is about that size, I run it suppressed and I have had zero issues with close to 8K on that upper.

I would generally agree with this, except for the gas port size. A carbine gassed 12.5" AR with a .078" port is aggressively gassed. With the addition of a silencers function in barrel length towards it's function to the action system is a bit much, even with the A5H4 buffer masses and known good springs. I would rather prefer some options in the .065ish" range for this use.

[tb-av]

Since the barrel was replaced and the problem started is it possible the bore is actually undersized?