The .45 ACP (,45 Auto)

The .45 ACP (.45 Auto)
By Chuck Hawks
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 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. Among civilian shooters, the .45 ACP is more popular today than it ever was.
As one would expect, there are plenty of reloading components for the .45 ACP. The most popular bullet weights are 185, 200, and 230 grains. The correct bullet diameter is .452", maximum COL is 1.275", and the MAP limit is 21,000 psi. .45 ACP reloads must be taper crimped. Medium to fast burning pistol powders generally work best in the .45 Auto.
The impressive 200 grain Speer "Flying Ashtray" can be given a MV of 823 fps by 8.5 grains of HS6 powder, and a MV of 956 fps by 9.5 grains of HS6. A 200 grain bullet makes a pretty good general purpose load for the .45 ACP, just as John Browning originally envisioned.
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.
The Speer Reloading Manual Number 13 shows that their 185 grain Gold Dot JHP bullet can be driven at a MV of 837 fps by 6.6 grains of W231 powder, and a MV of 954 fps by 7.4 grains of W231.
​The Speer 230 grain TMJ ("ball ammunition") bullet can be driven at a MV of 773 fps by 7.8 grains of HS6 powder, and a MV of 863 fps by 8.5 grains of HS6. All of these Speer loads used Speer cases and CCI 300 primers, and were tested in the 4.4" barrel of a SIG pistol.