It could be my eyes or possibly camera tricks but it looks like the fail to fire ammo got dented well but
the thing I am seeing is the primer looks to be seated deeper after the FTF.
maybe the anvil in the primer is not touching the bottom of the primer pocket and therefore needs a longer firing pin to set them off.
Reloading ammo sucks to a point. But I do not ever get FTF with my reloads and they are stupid accurate which puts the fun back into shooting.
I never did go shooting just to go through hundreds of rounds of ammo though. Unless it was a brass fail test.
Primers were set a little deep to begin with,and were getting fairly good dents from the initial strike.
I think the extended FP penetrates about .006 IIRC.
Thank you for testing and the good info. Although I currently don't shoot steel cased ammo, it is useful info to have. I apologize for the snobby replies.