I have a little dilemma with regard to a custom wildcat my gunsmith is almost done with. It’s an improved version of the 338 RUM. The shoulder is moved forward and a little case taper has been removed. I am going to have Neil Jones build custom dies but he needs brass that has been fired three times. Is there anything I can use to neck-size temporarily so I can get some of the brass run through the gun and sent off for the dies to be made? The fire-formed stuff won't fit into a normal 338 RUM die. Thanks.