the ".45" in .45 ACP refers to .45 inch diameter of the cartridge. the cartridge is the round or often called the "slug", "bullet", or "cap". some of those terms are not 'technically' correct, but for the purpose of general slang they will do.

currently (circa 1999), the .45 ACP continues to rank among the great cartidges of all time, both as a target around and as ammunition for general shooting purposes.

the .45 Automatic Colt Pistol was designed by John M. Browning at some point prior to 1911.

*see also Colt .45 Automatic.

A quick note of correction and history. The actual projectile part of a modern round of ammunition is called the 'bullet' (or 'ball', 'slug'). The term cartridge actually predates the all-inclusive ammunition concept. During the American Civil War, for example, the Springfield Rifle (the most widely-used single-shot muzzle-loader) was loaded using pre-packaged amounts of powder that came in wax paper - those were called 'cartridges.' The term has evolved to indicate a complete, ready to fire round.

The .45 ACP was originally designed and intended to be a cavalryman's weapon - this is why it emphasizes throwing large bullets relatively slowly. Accuracy (never the early M1911's strong suit) was not as important when you were shooting at horsemen, as a hit on either would suffice; if you did hit, you wanted the maximum stopping power, which indicated large, slower bullets.

The .45 Automatic Colt Pistol (hence ACP) cartridge (actual diameter .452 inch) was introduced in 1905 but only became widely popular when John Moses Browning and Samuel Colt designed and produced the semiautomatic pistol which was to become the Government Model 1911. The m1911 (so called because it was adopted in the year 1911) was chambered in .45 ACP after the .38 Long Colt which was until then the standard G.I. sidearm proved to be ineffective against an extremely determined attacker. These "extremely determined attackers" were mostly moro insurgents in the Philippines and at times were repeatedly shot with the .38 LC or sometimes even with the .30 Krag (a rifle round) but still were able to continue charging and injure/kill american soldiers. Although these moros would eventually die due to the blood loss brought about by multiple gun shot wounds, the non-instantaneous incapacitation proved to be fatal for american troops.

A quote from

It was the cartridge tests conducted by Thompson and Major Louis Anatole LaGarde of the Medical Corps in 1904 at the Nelson Morris Company Union Stockyards in Chicago that resulted in the adoption of the .45 caliber as the official U.S. Army handgun cartridge.

They tested various calibers on live cattle, deer, and human cadavers to determine the best load. From these tests it was determined that the .45 was the most effective cartridge for a handgun, but with reservations. In their report, they state:

"the Board was of the opinion that a bullet, which will have the shock effect and stopping effect at short ranges necessary for a military pistol or revolver, should have a caliber not less than .45". But they also said, "...soldiers armed with pistols or revolvers should be drilled unremittingly in the accuracy of fire" because most of the human body offered "no hope of stopping an adversary by shock or other immediate results when hit."

In response to the Ordnance Board’s specification, Browning designed the .45 ACP for the pistol he was submitting to the board. Browning's first loading was a 200 grain bullet running at 900 feet per second, but the Army wanted a larger bullet. Browning responded with the loading we have today, a 230mgrain bullet with a muzzle velocity of 830 feet per second.

The .45 ACP fought in every major conflict and continues to do so despite of the fact that the standard US Armed Forces sidearm is now the M9 Beretta 92FS chambered in the anemic 9mm NATO.

Should you ever consider to carry a gun for self defense the .45 ACP will never let you down as long as you do your part. Shoot and hit the bad guy. Today, as it was, and ever shall be, the .45 ACP is still the perfect cartridge for shooting damn dirty moro insurgents.

Log in or register to write something here or to contact authors.