A friend and I loaded up some black powder substitute in .45ACP and fired it in a WWII-era Colt 1911. Worked just fine.
Then, ginning like fools, we loaded up a box full and fired it through a M1A1 Thompson. GREAT fun, and we had black faces after.
We used a 9mm case-full of powder for the .45ACP case. Then put a bee's wax wad over it and loaded a 230-gr Lasermax lead bullet over that. There was no lead fouling and remarkably little powder fouling in the bores. The action of the Colt was filthy and the Thompson breach was REALLY filthy. Clean up took a while.
