Been playing with 223 case based AI's for quite awhile, solution to fireform FTF's is to use a more sensitive thin cup primer (CCI 400, 6 1/2, WSR) for the fireform load, then switch to 7 1/2's/BR-4's/450's or other magnum high pressure capable primer. Problem solved 100%. NOT a headspace or pin protrusion issue. .035"-.040" pin protrusion and 100% reliable primer ignition.

Didn't matter, .100" pin protrusion, heavy bullet jam, tight chamber fit and a 7 1/2 or 450 would have a high rate of FTF's and what appeared to be light strikes.