45 ACP is a rimless cartridge so no. I think the only time you can shoot 45 ACP in a 45 LC is in a revolver with the moon clip that grabs it at the base. Don't quote me on that, though. Hopefully someone more knowledgable on the cartridge can give you a good answer.
No you CAN NOT use 45 ACP in a rifle chambered in 45 Colt. The ACP is a rimless case and the Colt is a rimmed case. In SOME revolvers you can use both but the 45 ACP has to use the moon clips. These revolvers are specially made to use both rounds.
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.
Yepper. Made for use in the revolvers that HAD TO HAVE a moon clip to shoot 45 ACP....but with the AR round ( stands for automatic rimmed) ya just slipped them in like you would in a Long Colt revolver