The famous .45 Automatic Colt Pistol cartridge was designed by John Browning in 1905 for a prototype service pistol. The U.S. Army tested both the pistol and cartridge and requested some changes, including a heavier bullet (the original weight was 200 grains). Browning changed the bullet weight to 230 grains at 850 fps and the .45 ACP as we know it today was born. The Army adopted both the cartridge and the Browning designed Colt pistol in 1911 and both are still going strong today.

The .45 ACP case has a very slight taper from rim to case mouth of .007 inch. This is about half the taper of the 9mm Luger case and probably not enough to significantly enhance the feed reliability of a cartridge as fat as the .45.

The .45 ACP cartridge remained service standard with the U.S. Army until 1985, when it was replaced by the NATO standard 9x19 (9mm Luger). This set the record for longevity and it may never be broken. The .45 ACP served the U.S. well in WW I, WW II, Korea, and Vietnam. In the 1950's it became the favorite cartridge for the new sport of combat pistol shooting, so much so that the USPSA/IPSC rules were rigged in its favor.

The .45 has become so legendary in the U.S. that it is difficult to write about it honestly without offending some readers. It is an excellent cartridge for self-defense, but not the absolute best. The Colt 1911 Government Model is a fine pistol, but there are simpler, more reliable, higher capacity designs available in .45 ACP (as well as other cartridges). The .45 ACP did not provide the stopping power that saved U.S. servicemen from knife wielding natives in the Philippines in the early years of the 20th Century, that was the .45 (Long) Colt cartridge and the old Colt SAA (Peacemaker) revolver.

The original and still common 230 grain FMJ .45 bullet is not a 90% stopper, as was once widely asserted. Its actual one shot stop percentage is about 63% and that number is not significantly better than the percentage for the equivalent 124 grain 9mm FMJ bullet (about 62%). These are the facts, as Joe Friday used to say on the old TV series Dragnet, only the facts.

None of this is intended to belittle the .45 ACP, which is one of our best self-defense cartridges. Its best one shot stop percentage is 94% with Federal 230 grain Hydra-Shok bullets, which is a very high number. Other good .45 ACP loads are the Cor-Bon 185 grain JHP at 92%, CCI 200 grain JHP at 88%, Federal 185 grain JHP at 87% and Remington +P 185 grain JHP at 86%. Not all pistols will feed all loads and some, including Government Issue M-1911 pistols, may not feed anything but 230 grain ball (FMJ) ammo reliably. Modern pistols like the Glock and SIG are usually reliable with all modern ammo, but it is wise to shoot any .45 ACP pistol extensively with whatever ammunition is chosen for self-defense to verify its reliability.

Modern .45 ACP factory loads usually come with 185, 200, or 230 grain bullets, in JHP and FMJ styles. Unless you are stuck with a .45 pistol that will feed nothing else, use the ball ammo for practice and stick to JHP bullets for self-defense. Because 230 grain FMJ ammo is cheaper than JHP ammo and because the .45 ACP is an expensive caliber to feed under the best circumstances, many fans choose a good 230 grain JHP bullet for self-defense and practice mainly with cheaper 230 grain ball ammo. This avoids having to re-zero the pistol after every practice session. Anyway, most .45s have fixed sights, regulated for the 230 grain bullet.

The typical factory load for the .45 ACP uses a 230 grain bullet (either FMJ or JHP) at a published muzzle velocity (in a 5" barrel) of 850 fps with 370 ft. lbs. of muzzle energy. This load has a mid-range trajectory of .4" over 25 yards, 1.6" over 50 yards and 3.7" over 75 yards. Beyond that the fat, slow bullet is falling pretty fast, but not many people can hit reliably at long range with a .45 auto, anyway. The outdoorsman would be better off carrying something else.

As one would expect, there are plenty of reloading components for the .45 ACP. The Speer Reloading Manual Number 14 shows that their 230 grain Gold Dot HP bullet can be driven at a MV of 702 fps by 7.2 grains of HS-6 powder, and a MV of 799 fps by 8.0 grains of HS-6. These loads used Speer cases and CCI 300 primers and were tested in the 4.4" barrel of a SIG P220 pistol.

The .45 ACP has a reputation as being a hard kicking cartridge, difficult to shoot well. To an extent it is, because it throws a heavy bullet. If you make a .45 auto light enough for comfortable concealed carry, it kicks pretty hard. A gun heavy enough to dampen some of the recoil, like a Colt Gold Cup target pistol, is considered too heavy and bulky for daily concealed carry by most civilians. Some of the felt recoil may also be attributable to the ergonomics of the Colt Government Model pistol, which definitely does not fit every hand. (The Glock 21, for example, with its more relaxed grip angle has a reputation as a "soft" shooting .45).

People with small hands are liable to have trouble controlling any large frame auto pistol. This is one reason the .45 ACP has never been particularly popular as a police service cartridge, although modern .45 Autos, such as the Glock and SIG-Sauer, have made some inroads in the police market.

Another reason for the Colt 1911 / .45 ACP's limited popularity with police agencies is the fact that the Colt auto is a single action pistol that must be carried "cocked and locked" (chamber loaded and hammer on full cock, manual safety engaged) if it is to be gotten into action quickly from a holster. Cocked and locked carry gives many people the willies, including liability conscious police commissions. Modern pistols, like the double action SIG or "safe action" Glock, do not have this problem.

At least part of the reason for the .45's reputation for mediocre accuracy is due to the fact that John Browning's historic M1911 service pistol was designed to work under combat conditions and the tolerances are pretty loose. Nor was Government Issue .45 hardball ammunition loaded to the most stringent standards of accuracy. A standard GI .45 shooting hardball ammo is simply not a particularly accurate pistol, no matter how cool and experienced the shooter. However, a target grade .45, shooting target grade ammunition, is capable of shooting fine groups at 25 yards.

The .45 ACP is a fine old cartridge, not as good as its most ardent admirers believe, nor as bad as its most negative critics imply. The .45 Auto may not the best choice for many purposes, but it is in the upper echelon of combat pistol cartridges.