The Colt Government Model 1911: Thoughts on Parts Interchangeability

Everyone is familiar with Colt’s Patented Firearms Manufacturing Company and their excellent products, and the Model 1911 pistol certainly needs no introduction, being the official sidearm of the U. S. Armed Forces for over 70 years. While it may not be everybody’s favorite sidearm, the Government Model is easily the world’s most popular handgun for both self-defense and target competition.

Ninety years young, the 1911 has been manufactured by over 30 different firms, and that number doesn’t include all the clones and copies. The Model 1911 Government Model .45 ACP, designed by John Browning and produced by Colt, was adopted by our armed forces after an extensive trial and development period. It was chambered for the .45 Automatic Colt Pistol (ACP) cartridge. The original Colt automatic pistols—the Model 1900 and Model 1902—were chambered for the .38 Automatic Colt Pistol (ACP) Cartridge.

In 1929, the Colt’s Patented Firearms Manufacturing Company introduced a modified Government Model, the Super .38, chambered for the .38 Super Auto cartridge. In addition to the .45 ACP, the Government Model would eventually be chambered by the factory for the 9mm Luger, the .38 Super, the .38 Special mid-range, the 9×23 Winchester cartridge, the .40 S&W, the 10mm, as well as in some European calibers for export.

This pistol would also be manufactured in a National Match version, a shortened version, a lightweight shortened version, and a compact version. These were known as the National Match, the Gold Cup, the Combat Commander, the Commander, and the Officer’s ACP and Defender Models.

I’ve owned a Mark IV Series-70 Colt Government Model in .45 ACP and .38 Super Auto caliber for many years, and it was Bob Campbell’s article on the .38 Super in the October 2003 issue of American Gunsmith that got me thinking about the minor but significant differences between these pistols. The Ejectors: Dimensions and Differences The slide assemblies are not interchangeable, because the ejectors are not the same.

The .38 Automatic case is smaller than the .45 Automatic, and the .38 ACP ejector is wider toward the center than the .45 ACP. The overall width of the .38 Super ejector is .179 inch, and the .45 Auto is .139. The rim diameter of the .38 ACP/Super case is .405 inch, while the .45 ACP case rim diameter is .476. As you can see, there’s a difference of .071 inch between the two cartridge cases and .040 inch between the ejectors. Now we divide the .38 Super case-rim diameter in half, and we get .0355 inch.

The difference is pretty close to being equal (within .005), and the ejector dimensions probably vary. Remember, Mil Spec is plus or minus .002 inch. Some dimensions are fixed minus .002 to .005 inch. The step on the ejectors is also different. While the height of the step is the same at .135 inch, the .38 Super is .114 inch deep and the .45 ACP is .084 inch deep, which gives usa difference of .030 inch. The width of the vertical projection of the two ejectors is also different.

The .38 Super is .065 inch wide, while the .45 ACP is .055. Add .030 inch and .010 inch, and we have .040-inch difference. The Super ejector is .020-inch higher than the .45 ejector, which is a height of .230 inch for the .45 ACP and .250 inch for the .38 Super. The Super ejector has a .035-inch-deep relief cut on the back end for hammer clearance. The overall length of the standard GM ejector is .968 inch. They do not have a forward leg extension.

My Mark IV Series-70 Government Model .38 Super Auto does not have the extended ejector. These ejectors were originally Commander/Combat Commander ejectors, and I think were used in the Colt Series-70 Government Model 9mm. My Ed Brown .45 GM extended ejector has an extended leg of .090 inch, an overall length of 1.055 inches, the other dimensions being the same as the stock .45 GM ejector. These are not Commander ejectors.

The Commander ejector is similar to the .38 Super Auto GM ejector, but has a leg extension of .185 inch and an overall length of 1.132 inches. The overall height is .242 inch, while the step dimensions are .135 inch high by .099 inch deep. The vertical projection of the Commander ejector is .080 inch wide with a .040-inch hammer-relief cut. The overall width

45 ACP GM ejector, the .38 Super Auto GM ejector, and right the .45ACP Commander ejector. 45 ACP GM ejector, the .38 Super Auto ejector, and the .45 ACP Commander ejector. of the Commander ejector is .179 inch—the same as the .38 Super. Slide Peculiarities The ejector channel in the slides is also different. The Super Auto’s is wider toward the center of the pistol, but the offset that mates the step in the ejector is also closer to the center.

If you want to fit a .45 ACP slide onto the .38 Super frame, it can be done by milling the ejector channel wider and maybe a little deeper. At one time, I had an aftermarket M1911 aluminum frame, on which I installed a Springfield Armory 9mm conversion kit, and then fit a surplus GI slide to the same gun that way. Some GM .45 slides may fit the wider ejectors. After World War II, Colt introduced the Colt Commander Model in 1950.

This handgun had an aluminum frame, a shortened slide, and was offered in 9mm Luger, .38 Super Auto, and .45 ACP. This particular pistol uses the same type ejector and the slides may also be interchangeable. My model 1991-A1 Combat Commander .45 slide fits onto both the .38 Super GM frame and the.45 GM frame, but can’t be used there because the 1991-A1 is a Series-80 type. The Series-70 .38 Super slide fits the 1991-A1 Commander frame, but is too long for the frame.

The .45 ACP GM slide will not fit either the .38 Super Government Model frame or the Commander .45 frame. Early Colt GM .22 conversion units will not fit the .38 Super Auto. Conversion units made after WWII fit both Government Models (I think). Twenty-two conversion units made after 1970 will fit both GM pistols. My Series-70 Ace slide will fit onto both of my Government Models. The Service Model Ace uses a standard .45 ejector.

The Delta Elite uses a standard .38/9mm ejector, and the .40 S&W, 9mm, and the Compact use the Commander extended ejector. In 1970, Colt introduced the Combat Commander, a shortened, steelframe 1911 similar to the Commander. Since then, this nomenclature has been changed to Commander and Lightweight Commander. The wider ejector was necessary for the .38 Auto case to function in the Government Model, because the diameter is smaller and would miss the .45 ACP ejector. The reverse is not true.

The Commander ejector is universal in some ways, because both the .38 Super GM slide (the 9mm slide), and the .45 ACP Commander slide both fit this type ejector. The Commander ejector has along forward extension because the slide on these pistols does not recoil as far to the rear as the GM due to the shorter slide length. Conclusions and Afterthoughts A couple of things are important to remember: First, the M1911 was designed the way Army Ordnance wanted it.

The pistol was designed as a .45 caliber, with the .38 ACP chambering being a modification of that. As long as the 1911 Government Model pistol was standard issue, the Colt factory was not going to redesign it or manufacture a pistol that was not compatible with the ones already in service. Criticized for not having a firing-pin block or safety feature, one was designed for the Government Model in the 1920s. The Ordnance Department was not interested in a different model pistol.

The firing-pin safety would not be adopted by Colt until after the Government adopted the Beretta 92/ M9. This modification created the Series-80 Colt. ■