.45 Colt

The .45 Colt cartridge is a handgun cartridge dating to 1872. It began as a black powder revolver round developed for the Colt Single Action Army revolver, but is offered as a magnum level handgun hunting round in modern usage. This cartridge was adopted by the U.S. Army in 1873 and served as the official US military handgun cartridge for 19 years. It is sometimes, although incorrectly, referred to as .45 Long Colt or .45LC to differentiate it from the shorter .45 Schofield, as both were used by the army at the same period of time

History
The .45 Colt was a joint development between Colt's Patent Firearms Manufacturing Company, of Hartford, Connecticut, and the Union Metallic Cartridge Company of Bridgeport, Conn. Colt began work on the revolver in 1871, and submitted a sample to the U.S. Army in late 1872. The revolver was accepted for purchase in 1873.

The cartridge is an inside lubricated type. The rebated heel type bullet design of its predecessor, the .44 Colt (.452 -.454" diameter bullet), was eliminated, since it was an outside lubricated type, which would pick up dirt and grit during handling. The .45 Colt replaced the .50 caliber Model 1871 Remington single shot pistol and the various cap-and-ball revolvers converted to take metallic cartridges in use at the time. While the Colt remained popular, the Smith & Wesson M1875 Army Schofield Revolver was approved as an alternate.  The S&W revolver used the .45 Schofield, a shorter cartridge, which would work in the Colt, so Frankford Arsenal, then almost exclusive supplier of small arms ammunition to the U.S. Army, dropped production of the Colt round.  The M1875 round was replaced by the .38 Long Colt in 1892.  In 1909, the .45 M1909 round was issued along with the Colt New Service revolver. This round was never loaded commercially, and is almost identical to the original Colt round, except having a larger diameter rim. The rim is large enough that it cannot be loaded in adjacent chambers in the rod-ejector Colt model.

The .45 Colt remains popular with renewed interest in Cowboy Action Shooting. Additionally, the round has seen resurgence as a cartridge in handgun hunting and Metallic Silhouette Shooting competitions beginning in the 1950s with the introduction of stronger heavier framed handguns. It became the basis for rounds such as the .454 Casull.

Cartridge loads
The .45 Colt originally was a black-powder cartridge, but modern loadings use smokeless powder. The original black-powder loads called for 28 to 40 gr of black powder behind a 230 to 255 gr lead bullet. These loads developed muzzle velocities of up to 1000 ft/s. Because of this power and its excellent accuracy, the .45 Colt was the most-used cartridge at the time of its introduction, succeeding the .44 WCF (or the .44-40 Winchester). The .45 Colt never enjoyed the .44-40's advantage of a Winchester rifle chambered for it, allowing use of the same cartridge in both pistol and rifle. The reason was that early .45 Colt cartridges had a very minimal rim, and would not eject reliably. Currently manufactured brass has a rim of adequate diameter for such uses. Modern Winchesters, Marlins and replicas have remedied this omission almost 100 years after the fact, and the .45 Colt is now available in modern lever-action rifles. While this has been one of numerous arguments to explain the lack of a rifle chambered in .45 Colt, in fact, Colt would not authorize the use of their .45 Colt in other manufacturers’ arms. It required the expiration of those original patents for the .45 Colt to become available in a lever action or indeed in any other action rifle.

Today's standard factory loads develop around 400 ftlbf of muzzle energy at about 860 ft/s, making it roughly equivalent to modern .45 ACP loads. There are Cowboy Action Shooting loads which develop muzzle velocities of around 750 ft/s.

Some handloads and factory manufactured cartridges put this round in the same class as the .44 Magnum. These loads cannot be used in any original Colt Single-Action Army or replica thereof, such as those produced by Uberti, Beretta, the Taurus Gaucho, or the Ruger New Vaquero, as these guns are built on the smaller frame with thinner cylinder walls. These loads should be used only in modern large-frame revolvers such as the Ruger Blackhawk, Redhawk, Ruger Vaquero (erroneously referred to as the "Old Model" to differentiate it from the "New Model"), Thompson Center Contender or any gun firing the .454 Casull cartridge. Modern rifles with strong actions (such as the Winchester Model 1894, Marlin Model 1894, and new clones of the Winchester Model 1892) chambered for the cartridge can safely handle the heavier loadings.

Uses
Colt began work on their 1873 Single Action Army Model in 1871. Sample cartridges submitted for Army tests were made by UMC, using the Benet cup primers; commercial ammunition used the Berdan-type primer, followed by the more common Boxer priming. Original UMC loads used a 40 gr powder charge and 250 gr bullet. This was reduced to 35 gr of powder, and later, by the Army, to 28 gr.

The .45 Colt cartridge remains in use 151 years after its introduction. It is used as a hunting load on animals the size of deer and black bear. Heavier handloads will take the same range of big game animals as the .44 Magnum. Several two-barrel derringers are sold that are chambered in .45 Colt, and some of these derringers can chamber a .410 bore shotgun shell without any modifications being required. Revolvers chambered in .410 shotgun are usually chambered for the .45 Colt such as the Taurus Judge and the Smith & Wesson Governor. However, the most popular use for the .45 Colt today is in Cowboy Action Shooting, where the round is fired from either original or replicas of the 1873 Colt Single-Action Army.

Winchester, Marlin, Henry, Chiappa, Rossi, and other manufacturers produce lever-action rifles chambered in .45 Colt. Colt has resumed production of the Single-Action Army, and many SAA replicas and near-replicas as well as modern-design single-actions by Ruger are chambered for this cartridge.

Influence on other cartridges
The .45 Colt became the basis for the much more powerful .454 Casull cartridge, with the .454 Casull having a slightly longer and stronger case. Any .454 Casull revolver will chamber and fire .45 Colt, but not the inverse due to the Casull's longer case. The .460 S&W Magnum is a longer version of the .454 Casull and the .45 Colt. Likewise, .460 Magnum revolvers can chamber and fire the two lesser cartridges, but again, not the reverse.