I do make some 243 case's from 308, have for a long time. I simply take a 308 case and run it through a 243 die, has worked every time. If you wanted to do it in steps, you might consider some inexpensive 260 die instead of some special die. If I were to neck down in two pass's I believe the best way is to remove the expander nipple from the 260 or what ever you use die. A 25-308 die was a 25 Super and I'd think it would be awful expensive. I'm with the other's that in that case just buy up a whole bunch of new 243 case's.
