I've ordered a .45 Auto blank case forming die from www.ch4d.com/
The cases are formed from .308 Win cut to about 1.25". Obviously any case in the .308 or .30-06 family could work (Same head dimension). I'm thinking we might be able to scavenge spent .30-06 blanks from the Garands and use them too.
I think we can reload the .45 Auto blanks too. Might have to anneal the case mouths. I had no trouble resizing, decapping and re-crimping a few samples I got. I actually used my .260 Rem die for resizing, decapping and uniforming out the crimped mouth. I want to work the mouth as little as possible.
We're going to try Trail Boss first. I'm thinking that the bulkiness will help with ignition. Might try some floral foam in the case mouth before crimping to help hold the powder in place but I have some concern about fouling. Another idea is a dab of paint or nail polish to help seal the crimp. The barrel on the test gun (a repro Thompson SMG) has three 0.17" holes drilled lengthwise through the barrel, instead of a .45 bore.
This has been a fun exercise so far! I'll get some photos of the process, and a video of firing the gun, a little later.