Firing a bullet of approximately the same weight, the .45 ACP and .44 Magnum represent different approaches to cartridge design. The .45 ACP was designed for rapid, precision firing by police officers and soldiers. By contrast, the .44 Magnum is all about brute force, packing the maximum amount of energy into a single shot.
.45 ACP History and Overview
The .45 ACP is a ubiquitous cartridge with a long history. It was the round that drove the M1911, the standard United States Army sidearm for more than 70 years, including both World Wars and the Vietnam War. It was designed by the famous John Browning in the early part of the 20th century. While working for Colt's Manufacturing Company, Browning conceived of the round as a way to increase the stopping power of existing small arms, which had proved ineffective in the Philippine-American War.
.44 Magnum History and Overview
The .44 Magnum has a slightly more prosaic origin. Rather than coming to save the day in a military conflict, it was the result of experiments in hand-loading. Enthusiasts modified the earlier .44 Special. The result was an incredibly powerful, high-velocity round. It was made slightly larger than the .44 Special to prevent .44 Magnum rounds from being accidentally chambered. This cartridge has made an indelible mark on popular culture. "Dirty Harry" Callahan carried a ".44 Magnum, the most powerful handgun in the world," and it's a .44 Magnum that Robert De Niro's Travis Bickle draws when he asks, "You talkin' to me?" in the movie "Taxi Driver."
Power
The .44 Magnum has earned a reputation as one of the most powerful handgun rounds available for home defense or hunting. It's capable of taking down extremely large game. Depending on how it's loaded, the .44 Magnum delivers between 900 and 1,500 foot pounds of energy; by contrast, the .45 ACP's power ranges between 400 and 600 foot pounds. In recent years the .44 Magnum's supremacy has been eclipsed by other rounds, including the .454 Casuli, but its combination of power and charisma have kept it a common choice for people looking for high-power cartridges in hunting or home defense.
Uses
Ironically, it's the very power of the .44 Magnum that limits its practical usefulness. For hunters, or people who know they only need one shot, the .44 Magnum delivers a lot of energy. Its high recoil, however, makes it difficult when multiple shots in quick succession are needed. In these cases, the less powerful .45 ACP is ideal. Indeed the name, Automatic Colt Pistol, reflects its usefulness in repeating weaponry. Although the M1911 pistol was only semi-automatic, a number of submachine guns were also chambered in .45 ACP, including the M3 "Grease Gun" and the Thompson M1921 (and subsequent M1928 and M1) submachine gun — popularly the "Tommy gun," the archetypal weapon of Hollywood gangsters.