Ok, so I've wondered about this for a while and I just don't know the answer. I just bought a S&W Governor which shoots the .410, 45LC and 45ACP.. I have tons of 45ACP ammo for my 1911... but I just don't what the difference between 45 Long Colt and 45 ACP is.. I know the 45LC came out first back in the 1870s.. but why does the 45 ACP have a slightly smaller cartridge rim ? Sorry if this is a dumb question ...

Craig

First thing that's different is case length.

Google SAAMI specs, and it'll show all the measurements of both cases.

The 45acp has no rim, it's rimless. Are you saying you do not know what the two cartridges look like?

The 45 Colt is a long rimmed revolver cartridge originally made/loaded with black powder. The 45acp is short rimless and designed to have approximately the same power with smokeless powder made for automatic handguns.

Thanks FiremanJG.... I'll check that out....
- parisite - I know what the two cartridges look like, but just not sure why they designed the 45acp to be a but smaller in such a way that you need to use moon clips on the Governor .... sorry, I guess I was not really clear as to what I was really trying to find out... My thinking was when they first developed the 45acp, why couldn't they use the same circumference as the 45LC ? hope that makes sense...

The 45acp was not designed for a revolver. It was designed for a semi automatic pistol. 45 automatic colt pistol.

lharrell79 - oh ok.. so that makes more sense now.. thanks ! Since it was designed to be fed semi-auto it had to be designed to be fed and extracted differently... now I get it.. thanks again... I just don't know that much about different rounds , etc.. and there are soooooooo freaking many different ones out there with slightly different sizes, intended uses,etc...

Yes, and the .45 Colt was originally a black powder cartridge and had to have a lot of capacity and that accounts for its size.

Also the rim case causes feeding problem in automatics. They have to be stack forward of the previous case..So they can't be used in straight magazines or drum magazines. Such as used on Thompson and the old grease gun.

I will add a bit here to possibly answer you more completely. 45 LC was originally a black powder cartridge and was designed for use in older revolvers as stated from the late 1800's. It has relatively low pressure ratings so as not to blow up the older revolvers. It is a rimmed cartridge and is held in the cylinder by the rim and therefore spaces off the rim.
45 ACP came about from the Browning designed auto pistols. The story is that the Marines wanted a 1 shot manstopper in an auto pistol. what we have today is the result of John Brownings BRILLIANT design.
The 45ACP as stated is rimless.. or the diameter of the rim is the same or smaller than the case diameter. This is so it will feed through a magazine smoothly. When the cartridge enters the chamber it is pushed until the nose of the bullet is almost in contact with the rifling. So it spaces itself off the nose of the bullet. The rim is only in contact with the extractor and the face of the bolt/ breech.
This also makes extraction much smoother.

Ok so thats my answer I hope it helps

Read up on the .460 Rowland. It's enlightening but at the same time brings up more questions.

Even if you don't reload, the manuals give the history of all cartridges and discuss the design criteria. Very interesting stuff and to me must reading if one wants to understand guns and ammunition.

Wikipedia is not bad for a free service. It has history, specs, performance, etc.

http://en.wikipedia.org/wiki/.45_Colt

http://en.wikipedia.org/wiki/.45_ACP

45 ACP headspaces on the mouth of the case, not bullet.

Yes, it does. Ideally.

The interesting thing I dug up in reading about the .460 Rowland is that even though the case is a little longer than the .45 ACP case, the .460 pistol can fire .45 ACP cases because the extractor keeps the cartridge in place in spite of the fact that the case mouth is not providing headspace confinement. I've read opinions that the extractor actually provides headpspacing in a 1911 anyway, but I'm not sure I agree---at least not when ammo is of the correct dimensions. I often check my .45 ACP handloads for good dimensions by dropping them into the chamber of a 1911 barrel.

I suppose that if the taper crimp was way overdone, then either the extractor hanging onto the rim (in the 1911, at least) or the bullet engaging the rifling could serve as back-up headspacing, so to speak.

I understand your point and agree.....I can't see the extractor providing head spacing unless the dimensions are wrong. The slide would not close in many instances.

I too often check reloads by dropping them in a loose 45Acp barrel.

Issues happen with lead bullets as the diameter is larger and they must be seated properly to allow the shell to be head spaced correctly. This goes against the other opinions like the extractor.

Great explaination Blanco, thanks .. and thanks everyone for your feedback !

the guys have done a good job above. Now for some questions you might have about the S&W Governor which shoots the .410, 45LC and 45ACP.

S&W Governors use a chamber much like the Thomson Center contender and arus Judge which is a long throated 45LC for chambering the 410 which has dimensions close enough to work, so both can be used in the same gun when designed for it.

the 45AC has been used in revolvers since WWI when Colt and S&W made revolvers for Government which use half or full moon clips to hold the cartridge by the rim in the correct location for headspacing and firing in a revolver (not just falling into the chamber like it would in a 45LC gun). An added benefit of acting as speed loaders since 3 or 6 cartridges can be loaded or ejected at the same time. the Governor uses the same clips for the 45ACP.

I was reading my Lyman manual last night and discovered the 45 auto rim which was designed by peters post WWI for use in 45 acp revolvers without the use of moon clips. No idea if anyone actually makes it any more just thought it was interesting.

http://en.m.wikipedia.org/wiki/.45_Auto_Rim

Have shot and reloaded the 45 auto rim numerous times for a S&S 1917. The starline brass is good stuff.