Brutus
CGN Ultra frequent flyer
I have 2...a .375 and a .452, built both myself, one on a 700, the other on a Savage. Both use Arrowhead Precision LRMP Module Breachplugs. One has a swinglock die made from a piece of the barrel stub that both sizes and engraves rifling, the other just a smooth sizer.
Kudos to you friend! Sounds like very nice equipment!