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This one has me stumped...
SLR receivers and adjustable gas block. Elftmann trigger. I've tried combos of Proof (stainless) and Bartlein barrels with JP and Lantac BCG's, and a matched bolt with the Bartlein. Federal 120gr FMJ and 140g SP are showing cratering, flattened, and an occasional pierced primer. Barnes 120g TSX was fine.

Is Federal 6.5 loaded hot??

Suppressed or unsuppressed? Head space verified? Ejection is OK? Is the gas block properly adjusted? Do you have a chronograph to measure the FPS of the Federal vs the others?

Unsuppressed. Yes headspace verified. Haven't been watching ejection. Yes to GB. No chrono data.

A strong possibility is your firing pin isn't a good fit to your firing pin hole in the bolt. Think hotdog down a hallway.

Jack Dupp wrote: ↑November 16th, 2024, 12:04 am A strong possibility is your firing pin isn't a good fit to your firing pin hole in the bolt. Think hotdog down a hallway.

I hear you, though it seems odd it'd be the case with two separate BCG's, and on the Shilen a third matched bolt/pin that came with it.

Don't shoot Federal ammo, simple solution.

QuietM4 wrote: ↑November 16th, 2024, 11:44 am Don't shoot Federal ammo, simple solution.

Thought of this

But honestly, is this a known thing with Federal ammo, or is it an underlying issue with the firearm?

Could just be the Federal ammo, but I’ve never heard of any issues. If it was a mechanical/parts issue, it would do it with all ammo, not just the Federal….that is the common denominator.

QuietM4 wrote: ↑November 16th, 2024, 1:30 pm Could just be the Federal ammo, but I’ve never heard of any issues. If it was a mechanical/parts issue, it would do it with all ammo, not just the Federal….that is the common denominator.

I hear you. I'd rather it just work with everything that is within spec. I'd be fine with saying not to use X obscure brand if they were known to just make stuff that's too hot...but it's Federal. I'll explore it more though. Thanks for the input.

Are there any other high pressure signs (extractor / ejector marks, signs of case stretching, etc.?)

No clue what the cause is... but I can tell you what I would do to try to find the issue...
1) Pick one configuration of the gun - and confirm that it is in spec (check headspace / chamber - confirm with go / no-go gauges).
2) If you have a cartridge that you know and trust because you've shot a ton of it - preferably something that is a middle of the road cartridge - I'd take a box of it and tune the gas system to it as a baseline. Get the gun ejecting in the 3:00 - 4:30 ark and confirm no pressure signs, etc. If you DO have pressure signs or trouble getting the gun to group brass - stop and look more closely at the gun.
3) Given that it's 6.5 CM - not something obscure or super expensive - I'd buy a box of a bunch of different grades of ammo ranging from white box to good hunting stuff and including the Federal stuff that you are having trouble with - then get a chronograph and maybe a big tarp or two and go shoot it all. Record:
a) Velocity / SD / ES for each load
b) Where the brass is being thrown for each brand/load - direction and distance - take notes.
c) Pressure signs on the brass. If it were me - and I saw anything else go out of norm (velocity, or brass placement) I'd stop - and start recording each round individually and checking each case for pressure signs.
4) Compare your velocity data to both the box for that load - and to other similar products. Look for patterns - and for things that obviously break the pattern.
If you find that everything except the federal shoots fairly close to the advertised / expected velocities, and ejects in a pattern that is either "good" or perhaps consistent with what you are seeing in the velocity data - then you have your answer - it's the federal ammo. If you find that the negative signs are occurring across a variety of rounds - then look for the next pattern...

At the end of the day - the whole exercise is about changing just one thing until the issue is isolated.

Just my 2 cents.

FWIW, my ancient DPMS bolt and firing pin exhibited "cratered primers with commercial (not with surplus M80) .308/7.62mm ammo.
Never saw a pierced primer, but the crater bothered me. Got a JP high pressure bolt and the cratering vanished.
I put it down to a sloppy firing pin hole in the DPMS bolt. I would call it more an extrusion of the primer.

Update, it was the ammo. I tried seven different loads. The three Federals crated, the other four (Hornady, Barnes, Sig, & S&B did not).

Lion Armament LLC wrote: ↑December 12th, 2024, 9:46 pm Update, it was the ammo. I tried seven different loads. The three Federals crated, the other four (Hornady, Barnes, Sig, & S&B did not).

Interesting. I wonder if the Federal primers are somehow thinner, compared to what the other ammo mfgs use. It's been a while since I used Federal primers, but I never had any issues like you experienced.

Used to be the only primers that reliably worked in light revo actions were Federals. Seems they still are the thinnest.

Lion Armament LLC wrote: ↑December 12th, 2024, 9:46 pm Update, it was the ammo. I tried seven different loads. The three Federals crated, the other four (Hornady, Barnes, Sig, & S&B did not).

I’ll swing over and collect the defective ammo for ya. I won’t even charge you for disposal