Semi Bren Primer Flow

[TactAdv]

You have more problems with that ammo than you know. In each cartridge case shown the base metal of the case head is decomposed/eroded on the interior rim at the primer pocket opening. The non-uniform surface deformation/ inconsistency visible appears to be the result of corrosion or mechanical abrasion.

Are those reloads?? That ammo would fail any ISO verification check given at original manufacture. If you bought them loose in a brown cardboard box from ATK/Federal, they are "factory seconds", failed acceptance (scrap), that's what ALL the Federal labeled bulk "MILSPEC" is being sold commercially.

I'd start with some other ammo before you go on a wild goose chase with your gun.
-TomH