Hi
This how I got cheap dies for my 375 jdj. I got 444 brass... lubed a case and used a bar clamp held in a vise and using the hand screw part to force the lubed case into the barrel... Being very careful of the muzzle and chamber and used a dowel rod to tap them out...It was slow but I was only doing 50. After that I had basically fired cases. I then got a 378 weatherby die set, ground off some of both dies, ended up with a neck sizing die and one to put the bullets in with... Weird but it does work...So far. anyway!!! Be careful how much you grind off of them, I almost got too much on the first one I did.
Good luck
jim