Hi, I am currently building some cartridges for my 12.7x65R double rifle from Germany 1890's, you may check with cartridge collectors but chances are you will be doing the same as I, what I finally settled on with the help of some experts & freinds. I started with starline 45-90sharps cases & thinned the rims on the front side to desired thickness (I measured the primer pockets depth first & took whatever mat'l off the face to eliminate as much chamfer as possible, I next found a die (.375 Ruger) and necked the brass to what I needed, then took an old die & recut to get close enough to chamber mfor fire forming, then filled to capicty to where the bullet would seat with light compaction, weighed that charge & substituted 40% of that weight with 4198 & poly filler between the powder & bullet, then seated the bullet and am now ready for fire forming & then working up the load for velocity & regulating. I have also had to go this route with a 10.25x60R cape gun starting with .43 mauser brass & reforming. You can also send off a chamber casting made of cerosafe to CH4D and have them custom make dies for you. Good luck & have fun with it, it is quite satisfying to put one of these old guns back into service although can be time comsuming.

m4220