I would get a case gauge, highly doubtful that the projectile is hitting the lands and locking up the bolt, just doesn't happen unless you have supercrimp. Typically on this, when the factory case was sized, it was done incorrectly. The same happens on reloaded ammo when resized wrong. A case gauge will show this. Once the ram makes contact with the sizing die, lower ram and turn another 1/4" down on the sizing die, if this is not done cases will get stuck in the chamber, as well as on improperly trimmed brass, and yet again a case gauge will show this. I see this same issue all the time with 308 ARs.
Yes, no marks at all on the projectile suggesting ogive is not touching lands and if rammed into chamber I'd expect extraction and a spilled powder mess. These Federals run great in the M40A1 bolt gun so resizing seems kind of a double edged sword. A concern I have is if I start seating these factory rounds deeper then I will increase pressure.
I know that match rounds I load for single shot are extra long but not relevant to this magazine fed platform (currently).
Rather than resizing the Federal Match rounds would you guys think that Milsurp Match ammo spec at 7.62 X 51 in a 168gr or 175 gr. may work? In other words is it more likely case dimension / OAL from the .308 Match or a LMT chamber sizing issue?
Pure speculation without dimensional data but hoping for some experienced consensus.
Next question - which smiths in the valley can finalize diagnosis and who do you trust?