The 45 Colt, which is often loaded for cowboy action shooting, is an entirely different cartridge than the 45 ACP - and the 1917 revolver is chambered for 45 ACP. NEVER use 45 Colt ammunition in a 1917 revolver. But there is a legitimate way to avoid using clips on your ammo - read on.
The 45 Colt cartridge was introduced in 1873. It is sometimes erroneously called "45 Long Colt" or "45 Colt Long," but neither is correct. It is said that the "long" designation was tacked on by the US military at a time when they used two different .45-caliber revolvers, and the Colt guns of that period took the longer of the two types of ammo. It is completely different than the 45 ACP, and the two should never be interchanged.
I cannot fully chamber 45 Colt ammunition in my 1917 Colt revolver, which is good - but early specimens of this model did not have a step in the chamber, and 45 Colt ammo may go fully into the chambers on those guns. This could create a very dangerous situation - do not try it.
The 1917 Colt revolver was designed for, and accepts, 45 ACP (Automatic Colt Pistol) ammunition. This cartridge was the spawn of the legendary gun inventor John Moses Browning, when he developed a semi-automatic pistol in the early 1900s (this became the famous Model 1911). As outlined in the aforementioned article, 1917 revolvers were built simply to put more guns that would accept the 45 ACP into soldiers' hands faster.
Because the 45 ACP is a rimless cartridge, rounds of ammo are often clipped together so the empty cases can be easily extracted after firing. There is a rimmed cartridge that can be used without half moon or full moon clips in a revolver chambered for 45 ACP. Introduced in 1920, it's called the 45 Auto Rim, and is basically the 45 ACP with a rim added. It often featured soft lead bullets instead of the jacketed pistol bullets normally found in 45 ACP, to avoid undue wear on the soft barrels of 1917 revolvers.
Some sources call the 45 Auto Rim obsolete, but although this ammo may not be easy to find at your local Wal-Mart, it can certainly be found at press time from a number of sources, even if you have to order it online.
- Russ Chastain