For the 444-Biggun, I'd just make a couple expanding arbors like I posted in reply #171. You have to anneal the case, but they worked great on 223 to 357 and they should do even better on 30 to 429. If you cut them off at the shoulder you may be able to get away without annealing, although I still would. I didn't have good luck fire forming when I expanded the neck and left the case hour glass shaped. A full power 357 mag load did not expand the hourglass shape from the case. I started with wax, but ened up using real bullets as the wax was messy and wasn't letting the pressure build up enough. It took a 357max load to iron it out. I think it was because the case the pressure drops off so fast in a straight walled case v/s a bottle neck. The two expanders opened up the case enough that I was able to load a hotter 357 max load as a starting load. Then once fire formed, I was able to step up to 357AR pressures. I also found that the shoulder which was now the case mouth was all over the place as far as thickness went. Some were under my target .010" thickness, and some were thick enough to prevent them from chambering. I think the reaming approach will really pay off. I lathe turn mine and that is a PITA. I just may have to make up a case reamer for it.