The .38 Super Auto and .38 Auto (.38 ACP)

By Chuck Hawks

Colt introduced the .38 Auto (also known as the .38 ACP) in 1900, along with the Colt .38 Automatic Pistol, which was designed by John Browning. Colt hoped that this combination would be accepted by the US military as the replacement for the .38 Long Colt service revolver then in use. However, the military decided that they wanted a .45 caliber service pistol, so Colt and Browning had to go back to the drawing board. The result was the legendary Colt Government Model 1911 pistol and the .45 ACP cartridge, but that is another story.

The .38 Auto is probably most often associated with the Colt Model 1902 pistol, which sold fairly well in the civilian market. The .38 Auto was factory loaded with a 130 grain FMJ bullet at a muzzle velocity (MV) of 1040 fps and muzzle energy (ME) of 310 ft. lbs. Factory loaded ammunition was available almost to the end of the 20th Century. The .38 Auto is listed in the ammo section of my 1995 Gun Digest with a footnote that it had been discontinued.

The .38 Super was introduced in 1929 in the famous Colt Government Model 1911 auto pistol. The Government Model was much stronger than the earlier Colt .38 Auto pistol, and could handle more pressure. So the .38 Auto case was loaded to higher pressure (33,000 cup) to boost performance. The result was the .38 Super Auto, at the time of its introduction the most powerful auto pistol cartridge in the world.

Note that externally the .38 Super cartridge looks identical to the .38 Auto (except for the headstamp). .38 Auto ammunition may be fired in .38 Super guns, but it may not operate the slide. .38 Super ammo should never be fired in .38 Auto pistols; it is way over pressure for these guns. In 1974 the Shooting Industry mandated that a +P be added to the headstamp of .38 Super ammunition to help differentiate it from .38 Auto ammunition. The +P still appears on .38 Super cases, even though there has never been a low pressure .38 Super load, and the .38 Auto has been discontinued.

Colt is the only major American gun maker who has produced .38 Super pistols. Springfield Inc. has imported pistols in .38 Super under their brand name. A few European companies (Star is probably the best known) have turned out copies of the Model 1911 pistol over the years, and some of those have been chambered for the .38 Super cartridge. It is possible that some of the myriad of small (and not so small) semi-custom gun makers that make their livings from cloning the 1911 pistol have built .38 Supers. Model 1911 copies in .38 Super also may have been turned out in South America or other places. I understand, for instance, that the .38 Super was quite popular in Mexico at one time. Anyone hankering for a .38 Super pistol should be able to find one.

The .38 Super's ballistics are fairly impressive. It has been compared to the .357 Magnum revolver cartridge, but in reality it is closer in performance to a medium velocity .357 load than a full power magnum. Still, the .38 Super is one of the most powerful and flat-shooting cartridges available for autoloading pistols.

Remington and Federal do not load for the .38 Super, but Winchester does. Winchester factory loads for the .38 Super include a Super-X load and a less expensive USA brand load. The Super-X offering advertises a 125 grain Silvertip bullet at a MV of 1240 fps with 427 ft. lbs. of ME. This is the factory load to use for personal defense or in the field. The economical USA brand ammunition is great for practice and is loaded with a 130 grain FMJ bullet at a MV of 1215 fps and a ME of 426 ft. lbs.

The .38 Auto and .38 Super both use standard .355" (9mm) diameter bullets, so there are plenty of choices available to the reloader. Pistols chambered for the old .38 Auto should probably be retired, but any reloader with a .38 Super pistol can turn out very effective loads using modern JHP bullets.

The Speer Reloading Manual Number 13 shows that 7.5 grains of HS6 powder can drive their 124 grain Gold Dot bullet to a MV of 1134 fps, and 8.3 grains of HS6 can drive the same bullet to a MV of 1245 fps. These loads used Winchester cases and CCI 500 primers, and were tested in the 5" barrel of a Colt pistol.

The .38 Super should have been more popular than it is. It hits as hard as the .45 ACP, shoots flatter, kicks less, and .38 Super pistols carry an extra round or two. This has made the .38 Super popular in USPSA/IPSC action shooting competition, which is dominated by 1911 style pistols. But it never really caught on with the general public.

That may be due to its reputation for rather poor accuracy. The .38 Super is a semi-rimmed cartridge, meaning that it looks like an ordinary rimless cartridge, but its rim actually extends slightly beyond the case body. The purpose of this was to headspace the cartridge on the slight rim, but the miniscule rim led to poor headspacing and degraded accuracy. It took Colt decades to fix the problem by simply cutting their chambers to headspace on the case mouth (like most other auto pistol cartridges) instead of the tiny rim. All Colt Government Model .38 Super Auto pistols made since 1988 headspace on the case mouth and deliver accuracy comparable to the same gun in .45 ACP caliber.

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Copyright 2002, 2012 by Chuck Hawks. All rights reserved.