I have two double rifles in the above calibers. I am going to use 10.3x60R brass in the 400 and have Bertram brass for the 500/450 magnum. The new cases fit fine in the double rifles. I don't want to wait 6 months and pay hundreds of dollars for dies. Are there any easily available dies that I can use to neck size and seat the bullets? An example would be using .458 Winchester dies to load .450 3 1/4 straight, as long as full length resizing isn't needed. Obviously need the correct size for the bullet diameter. Am I barking up the wrong tree?
