Compared: the .45 ACP and .45 Colt

By Chuck Hawks

American Handgunners have had a love affair with .45 caliber handguns dating back at least to percussion revolvers (the ".44's" actually fired .451 inch balls) and black powder cartridges. The .45 Colt, also known as the .45 Long Colt to distinguish it from the shorter version chambered in S&W revolvers, was the black powder revolver cartridge most responsible for this from 1873 to 1911. The original black powder loads launched a 255 grain bullet at about 930 fps, making the .45 Colt the most powerful handgun cartridge of its day. With muzzle energy (ME) of 490 ft. lbs., this was a serious man-stopper. The .45 Colt served as the standard U.S. Army service cartridge from 1875-1892. It was replaced as service standard in 1892, when the .38 Long Colt was adopted by the Army. However, the .45 Colt was recalled to service during the Philippine Moro insurrection, when it was discovered that the rather anemic .38 Colt lacked adequate stopping power.

After that experience, the U.S. military decided they needed a .45 caliber service pistol and they wanted it in autoloading form. (The German Army had adopted the Luger autoloading pistol in 1908.) The adoption of the Colt Government Model service autoloader and the .45 ACP cartridge by the U.S. military in 1911 soon made the .45 ACP the most popular of our domestic .45's. Today, the .45 ACP cartridge remains the darling of big bore defensive pistol advocates.

However, the .45 Colt successfully made the transition to smokeless powder and remained popular in single action Colt Peacemaker revolvers, replica Peacemakers and S&W double-action revolvers. When Sturm Ruger chambered their robust Blackhawk revolver for the .45 Colt cartridge and Thompson/Center offered their very strong Contender single shot pistol in .45 Colt, it further broadened the old cartridge's appeal. The Blackhawk's cylinder was fatter than a Colt SAA cylinder, with consequently thicker walls and could safely be loaded to higher pressure and velocity than Colt or S&W revolvers and replicas thereof. These "+P" .45 Colt loads are not far behind the magnum revolver cartridges in power.

Today there are .45 Colt +P factory loads from some of the specialty ammo companies that are intended for use only in Ruger revolvers and T/C pistols. Most reloading manuals have special .45 Colt sections listing higher pressure loads specifically for use in Ruger Blackhawks and T/C single shot pistols.

Meanwhile, the .45 ACP has evolved with the advent of 185-230 grain JHP bullets that will feed in 1911 pistols and are for more effective stoppers than the traditional 230 grain ball (FMJ) bullets. In addition, .45 ACP +P loads are being offered by some of the commercial ammunition makers.

A variety of standard pressure loads are offered by almost all of the major U.S. ammunition manufacturers in both calibers and there are +P factory loads available for both. It is time to compare these two traditional American .45's.

The .45 ACP (.45 Auto)

The famous .45 Automatic Colt Pistol cartridge was designed by John Browning in 1905 for his 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.

The .45 ACP is a straight wall, rimless cartridge intended for use in autoloading pistols. Its rim diameter is .480", its base diameter is .476" and its neck diameter is .473". The case length is 0.898" and the maximum overall cartridge length is 1.275". The .45 ACP uses .451" diameter bullets and standard large pistol primers. The SAAMI maximum average pressure (MAP) is pegged at 21,000 psi.

Not all .45 ACP pistols will feed all loads and some, including Government Model 1911 pistols, may not reliably feed anything but 230 grain ball (FMJ) ammo. Modern .45 pistols, such as the Glock and SIG, are designed to function correctly with JHP ammo, but it is wise to shoot any .45 ACP pistol extensively with whatever ammunition is chosen for self-defense to verify its reliability.

.45 ACP factory loads usually come with 185, 200 or 230 grain bullets in JHP and FMJ styles. .45 ACP ammo is loaded by virtually all ammo manufacturers and widely distributed. Unless you are stuck with a 1911 pistol that will feed nothing but ball ammo, use JHP bullets for self-defense. Because 230 grain FMJ ammo is cheaper than JHP ammo, most shooters practice with ball ammo to save money.

The .45 Long Colt

The .45 Colt has remained a popular revolver cartridge throughout its long history. It is fun to shoot, not nearly as punishing as a .44 Magnum, but a lot more effective than a .44 Special. There are many revolvers available in .45 Colt, but the best and most popular are probably the Ruger Blackhawk and the Colt SAA (Peacemaker). Both are good guns, but only the Blackhawk is rated for +P ammunition.

Physically, the .45 Colt is a typical, straight wall, rimmed revolver cartridge. Its rim diameter is .512", its base diameter is .480" and its neck diameter is .476". The case length is 1.29" and the overall cartridge length is 1.60". The .45 Colt uses .452" diameter bullets and standard large pistol primers. The SAAMI maximum average pressure is pegged at 14,000 psi, while .45 Colt +P loads are usually loaded to a MAP of about 25,000 psi.

This is a big case with a lot of powder capacity (more than the .44 Magnum), which makes high performance cartridges easy to load and popular among shooters with Ruger Blackhawk revolvers. The Hornady Handbook, 9th Edition, for example, lists maximum +P loads using 240 grain bullets at 1450 fps, 250 grain bullets at 1350 fps and 300 grain bullets at 1300 fps for Blackhawk revolvers and T/C single shot pistols. These are .44 Magnum power level hunting loads and they are not fun to shoot! Such loads are far in excess of what can be achieved using the smaller .45 ACP case.

The Comparison

To keep this comparison valid, we will select a standard pressure and a commercial +P load in each caliber, using bullets in the 200-230 grain range. We will compare these loads in velocity, kinetic energy, trajectory and recoil. Maximum .45 Colt reloads for Ruger Blackhawk revolvers using 240 grain and heavier bullets are well beyond normal .45 ACP and .45 Colt performance levels and will not be included in this comparison.

Because both cartridges use .451-.452 inch diameter bullets, there is no difference in bullet cross-sectional area. Consequently, cross-sectional area will not be a factor in this comparison.

Given bullets of the same weight, sectional density is also the same. Normal bullet weights range from 185-230 grains (SD .130-.162) for the .45 ACP and 200-300 grains (SD .149-.210) for the .45 Colt. When loaded with bullets heavier than 230 grains, the .45 Colt has the advantage in sectional density and therefore, other things being equal, bullet penetration.

Standard pressure .45 ACP factory loads typically launch a 230 grain bullet at a muzzle velocity (MV) of 850-890 fps. To represent such loads, we will use the economical Federal American Eagle version, which launches a 230 grain FMJ bullet at a MV of 890 fps. For our +P load we will use the Speer Gold Dot factory load that launches a 200 grain JHP bullet at 1080 fps. The ballistics of these .45 ACP loads was developed in five inch barrels.

To represent the standard .45 Colt, we will use the Federal American Eagle load using a 225 grain JSP bullet at the typical MV of 860 fps from a 4 inch vented test barrel. For our .45 Colt +P load we will use the Cor-Bon 225 grain DPX load launching a 225 grain Barnes XPB hollow point bullet at 1200 fps from a 7.25 inch test barrel.


Velocity is important for initiating bullet expansion and it is the most important factor in calculating kinetic energy. Higher velocity flattens trajectory, making hitting easier at extended ranges and particularly at unknown ranges. Here are the velocities in feet per second (fps) of our comparison loads at the muzzle (MV), 50 and 100 yards.

        .45 ACP, 230 gr. Federal FMJ: MV 890 fps, 860 fps at 50 yards, 820 fps at 100 yards.

        .45 Colt, 225 gr. Federal JSP: MV 860 fps, 830 fps at 50 yards, 800 fps at 100 yards.

        .45 ACP +P, 200 gr. Speer GD-HP: MV 1080 fps, 994 fps at 50 yards, 930 fps at 100 yards.

        .45 Colt +P, 225 gr. Cor-Bon DPX: MV 1200 fps, 1080 fps at 50 yards, 998 fps at 100 yards.

As you can see, our comparison .45 ACP standard pressure load is slightly faster from the muzzle to 100 yards, holding a modest 30 fps advantage at 50 yards. However, the .45 Colt +P load is significantly faster than the .45 ACP +P load at all ranges. At 50 yards the .45 Colt +P has an 86 fps advantage and, in addition, its bullet is 25 grains heavier.


Kinetic energy is defined as the ability to do work. In this case, the "work" involved is primarily powering bullet penetration and expansion. Both are, of course, necessary for lethality. Here are the energy figures in foot-pounds (ft. lbs.) for our comparison loads from the muzzle (ME) to 100 yards.

        .45 ACP, 230 gr. Federal FMJ: ME 405 ft. lbs, 375 ft. lbs. at 50 yards, 345 ft. lbs. at 100 yards.

        .45 Colt, 225 gr. Federal JSP: ME 370 ft. lbs, 345 ft. lbs. at 50 yards, 320 ft. lbs. at 100 yards.

        .45 ACP +P, 200 gr. Speer GD-HP: ME 518 ft. lbs, 439 ft. lbs. at 50 yards, 384 ft. lbs. at 100 yards.

        .45 Colt +P, 225 gr. Cor-Bon DPX: ME 720 ft. lbs, 583 ft. lbs. at 50 yards, 498 ft. lbs. at 100 yards.

Due to its slightly higher velocity and slightly heavier bullet, the standard pressure American Eagle .45 ACP load develops a bit more energy at all ranges than the standard pressure .45 Colt load. The difference is only 30 ft. lbs. at 50 yards, which is not enough to make much difference in stopping power.

However, our .45 Colt +P load hits noticeably harder than our .45 ACP +P load at all ranges. The difference is 144 ft. lbs. at 50 yards, which should make a significant difference in stopping power.


The .45 Colt and .45 ACP were developed for personal protection and neither is a long range cartridge. However, in the real world, not every target is engaged right off the muzzle, so bullet drop comes increasing into play as ranges increase. For most purposes, I would suggest a 25 yard zero for both of these cartridges. This will put the bullet around two inches low at 50 yards with standard pressure/velocity loads, which means that no hold over is ordinarily necessary at that distance.

The Federal and Speer ammunition catalogs base their handgun trajectory information on a 25 yard zero and for comparison purposes we will use 25 yard figures. Here are the trajectory figures (in inches) for our selected loads for a gun equipped with iron sights.

        .45 ACP, 230 gr. Federal FMJ: +/- 0" at 25 yards, -2.0" at 50 yards, -15.0" at 100 yards.

        .45 Colt, 225 gr. Federal JSP: +/- 0" at 25 yards, -2.2" at 50 yards, -16.1" at 100 yards.

        .45 ACP +P, 200 gr. Speer GD-HP: +/- 0" at 25 yards, -1.1" at 50 yards, -10.2" at 100 yards.

        .45 Colt +P, 225 gr. Cor-Bon DPX: +/- 0" at 25 yards, -0.95" at 50 yards, -8.6" at 100 yards.

With standard velocity loads, there is no practical difference between the trajectories of our two cartridges; at 50 yards the difference amounts to only 0.2 inch in favor of the .45 ACP. Even with +P loads, from the muzzle to 50 yards there is no worthwhile difference. At 100 yards, the .45 Colt +P load has 1.6 inches less drop than the .45 ACP +P.


More recoil is always bad. It makes accurate bullet placement more difficult by increasing flinching and increases the recovery time required between shots. Here are some approximate recoil energy (ft. lbs.) and velocity (fps) figures for our comparison loads when fired in 2.5 pound handguns.

        .45 ACP, 230 gr. bullet at 890 fps: 7.2 ft. lbs; 13.6 fps

        .45 Colt, 225 gr. bullet at 860 fps: 6.9 ft. lbs; 13.3 fps

        .45 ACP, 200 gr. bullet at 1080 fps: 7.9 ft. lbs; 14.3 fps

        .45 Colt, 225 gr. bullet at 1200 fps: 12.1 ft. lbs; 17.6 fps

As revealed by these figures, most shooters are unlikely to notice the difference in recoil between these two cartridge when shooting standard pressure loads. Both are relatively mild. The .45 Colt's advantage is only 0.3 ft. lbs. less recoil energy and 0.3 fps less recoil velocity. If you can handle one, you should be able to handle the other.

The .45 Colt +P load, being significantly more powerful than the .45 ACP +P load, generates noticeably more recoil. Here, the .45 ACP has 4.2 ft. lbs. and 3.3 fps less recoil.


The most obvious difference between these two .45 caliber cartridges is the .45 Colt was designed for use in revolvers and the .45 ACP was designed for use in autoloading pistols. Revolver fans will gravitate to the .45 Colt and semi-automatic pistol fans will need to go with the .45 ACP.

With standard pressure loads there is little to choose between the two cartridges. Either is very good for personal protection out to about 50 yards when loaded with expanding bullets designed for the purpose. On the other hand, neither standard pressure cartridge has the power or flat trajectory normally recommended for big game hunting.

If you own a Ruger Blackhawk or some other very strong handgun and want to shoot +P loads, the bigger .45 Colt cartridge has a worthwhile performance advantage over the .45 ACP. Indeed, .45 Colt +P loads are considered satisfactory for moderate range hunting of CXP2 game, making the .45 Colt the more versatile cartridge.

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Copyright 2013 by Chuck Hawks. All rights reserved.