flash hole diameter, I have 45 ACP cases that use small pistol primers, all the 45 ACP cases that require small pistol primers have large diameter flash holes, all the 45 cases with large flash holes have head stamps that include ‘NT’, I do not load them, I could, I don’t.
I have a flash hole gage, from the old days, the tool is not something that is used everyday, but for those that measure before and again after and are wondering about the effect high pressure has on cases, the flash hole gage is a good place to start.
I acquired a few 45 ACP cases at the range, after punching the primers I turned all of them over and measured the diameter of the flash hole, the ‘NT’ cases allowed the gage to fall through. The large flash holes cases with small primers are are a night mare for commercial reloaders, the cases require separating first, then if the reloader decides to reload the small primer cases the equipment must be changed.
The primers are more user/environmentally friendly, as in without lead.