Looks like the only way to get your brother to listen now is to beat him up.
Smith and Wesson made a very collectable revolver that used both (with clips), I have one. Lets add some more mud to the mix. There is the 45 auto rim as well.
probably won't shoot in the first place as there wouldn't be anything to headspace off of. There's also a difference in the loaded diameter as the "acp" case is smaller.
gary
So you are correct newmexkid. Looks like the only way to get your brother to listen now is to beat him up. Thats usually what I do to my brothers.
I think you might have transposed a few numbers there...Since a little after WWII the 45 Colt bores have been standardized to shoot .542 Jacketed bullets. The 45 ACP uses .451 Jacketed bullets. With cast lead bullets most 45 Colts shoot well with .452 but some do need up to .545. Most 45 ACPs shoot best with .452 cast bullets.