Putting together this 40-72 H Rolling Block.
The fast twist barrel I was getting made in Brisbane is not going to happen it seems so I have put in a GM 16 twist I had on hand. The reamer came so its chambered now and I sized cases to fit with a die I made with that reamer.
Now I want to fireform some cases to see if the neck dimensions change.
My Jim mould came and I cast a bunch of boolits but dont really want to waste them fireforming.
Will BP and a wad fireform the neck or will it need the pressure buildup from a boolit to blow the necks out?
These will only be seated in 1/8 or 3/16 or so.
I was hoping a poly wad right at the mouth would do the trick. I have some cheap Spanish BP on hand so I can use a case full.