I doubt the problem is the OAL of the cartridge. When you say the head will not enter the gauge, are you referring to the rim end of the case or the bullet? It sounds more like your not getting the case sized down enough towards the rim of the case.I'm resurrecting this thread because I loaded some LRN at 1.250 and they bottom out in my case guage. The head will not enter the guage! The shoulder rim of the bullet seems to be resting on the lip in the guage. I also loaded some 200 gr LSWC at the same OAL, with the same effect. Both rounds seem to chamber ok. I'm going to field strip my Kimber next and see how they fit in the chamber. I've always thought the guage was gospel.