It's extremely rare that a 5.56 chamber be the cause of lost primers, and the gas system has pretty much nothing to do with it.
Primer unseating happens before the projectile reaches the gas port, but the more violent ejection associated with a suppressor will cause a loose primer to be more likely to actually fall free of the case.
If high pressure is suspected, examine the cartridge case head. High pressure will be evidenced by a heavy, sharp extractor ledge mark; a shiny, sharp ejector smear; and a noticeable raised ridge around the firing pin crater in the primer. Test a few different ammunition types and manufacturers. There is a reason that duty use ammo has aggressively staked primers (see especially Mk262 Mod 1, M855A1, and the Black Hills "Optimized" 70 and 50gr TSX).
I have seen lot to lot variation in many ammunition types, and I would not at all be surprised if overseas manufactured ammunition sold onto the US commercial market showed similar variation.