What's the difference

[GaryM]

The .45 ACP is for an autoloading weapon, the case length is .898 inch.
The .45 Colt is used in revolvers and carbines, the case length is 1.285 inch. RedRocker is correct, it is the same as the .45 Long Colt. Probably called Long Colt to distinguish it from the much shorter .45 ACP which, by the way, is also a rimless case.
Here is a link that may be informative. .45 Colt (.45 long Colt)

You can shoot .45 ACP rounds in your revolver if you use "half moon clips" or "full moon clips".Product: Full moon Clip for 45ACP

And one of these is right handy: http://images.google.com/imgres?img...-a&rls=org.mozilla:en-US:official&hs=aTw&sa=N

 

[Soundguy]

Moon clips not work in those? let you use that cheapy 45 acp in the night court judge....

soundguy