Moon Clips: What Are They and How Do They Work

When the United States was preparing to enter World War I, it was desperately short of material, jumping from a 30,000-man army to a projected 1-million-man force. Colt and other contractors could not fill the need for the issue handgun — the 1911 .45 Government Model. Both Colt and Smith & Wesson had production capacity geared up. Since the .45 automatic cartridge does not have a cartridge case rim, the ejector star could not eject the cartridge. S&W developed a thin sheet-metal clip to take the place of the cartridge case rim, neatly solving the problem of using the cartridge in a revolver. The moon clip was born, providing the necessary .05-inch headspace. There was now a single cartridge for both the automatic and the revolver in the supply chain.

What Is a Moon Clip?

Moon clips are devices for holding cartridges as they are loaded, fired and unloaded in a revolver. As mentioned above, the clips allow proper headspace and ejection with cartridges not originally intended for the revolver. For example, the 9mm Luger, .38 ACP, 10mm auto and .45 ACP do not have a cartridge case rim but rely on the case mouth for headspace. It isn’t difficult to chamber a revolver to accept these cartridges, but it is difficult to design a revolver that will properly eject a cartridge without a case rim. The moon clip solves these problems and offers several tactical advantages. There are also drawbacks, however, mostly related to the cartridge itself.

I have never read that speedloading was part of the design envelope. But it did result in the fastest revolver to load and unload ever manufactured. After the war, many of the 1917 revolvers were declared surplus. Most shooters did not want to use moon clips. While great for combat, they were an aggravation for day-to-day use.

A new lease on life came with the sport of bowling pin shooting. Pin shooters found the hard-hitting .45 ACP with proper handloads was the trick. The smooth rolling action of the S&W Model 625 proved a winning combination. However, all was not perfect. The .45 ACP is a short cartridge. The 625 is basically a .44 Magnum-sized handgun. The long jump from the chamber to the barrel throat resulted in poor accuracy with jacketed bullets. Sometimes there were misfires when the revolver was fired without moon clips. Light loads might even back up and tie the gun up. The accuracy problems are addressed by handloading long, heavy SWC bullets. While interesting, the revolvers demand careful load selection and proofing for reliability.

How to Use Moon Clips

With a conventional revolver, the barrel must be pointed upward to unload the cylinder. If you are not careful, a case may become trapped under the ejector star. With the creation of clips, though, simply hit the ejector rod and the half-moon clips and cartridges are ejected. A neat

trick no matter the angle. Next, slap loaded moon clips in. You are ready to go. The barrel need not be pointed downward at as severe an angle for loading. The modern full moon clip by Wilson Combat holds a full load of six cartridges. While the original set of two moon clips were faster than any conventional revolver, the modern six-shot moon clip is even faster.

There are also 9mm revolvers that use moon clips. I have experienced tie ups in the 9mm revolver with the bullets jumping the case. Revolver cartridges feature a bullet with a crimping groove and also a cannelure in the cartridge case. The forces of recoil drive the bullet forward. Factory cartridges are very reliable. The problem with the 9mm only occurred with certain types of ammunition. If you use a 9mm clipped revolver, be certain to proof the piece with extensive firing.

Moon Clip Revolvers Now

A sensation a few years ago was the Ruger GP100 in 10mm. This is among the finest combinations for personal defense I have tested. The revolver is accurate, and the problems with 9mm and .45 ACP reliability seem to have been addressed. The Ruger features a redesigned moon clip. The old clips were rigid and difficult to reload, demanding special tools. The new moon clip design gives a bit and is easy to load and unload. I like the Ruger 10mm a great deal. It is a mid-sized revolver that offers plenty of power and rapid reloading.

A modern rendition of the moon clip revolver covers all the bases and renders any criticism moot. Taurus offers the seven-shot 692 revolver in .357 Magnum. The Tracker may be fired with either .38 Special or .357 Magnum ammunition. Press a plunger in the side of the revolver frame and you may quickly change out to a 9mm cylinder. I have fired the Taurus extensively. There seems to be little to no accuracy penalty when using inexpensive 9mm ammunition. The moons clips are easy to load and unload and offer a very rapid speedload at all angles. If you opt for the 9mm with moon clips, you have a revolver faster than any other to load and unload. The 9mm isn’t as strong as the .357 but has a light recoil option for most shooters.

A final option is a modern one. Custom gunsmiths such as Gemini Custom offer modifications to existing revolvers. You may have your conventional .38 Special or .357 Magnum revolver modified to accept moon clips. The result is the advantage of a rapid reload without resorting to an automatic pistol cartridge. For those preferring the revolver, this is a great option, making for excellent combat ability. The moon clip revolver was designed more than 100 years ago and today is more popular than ever. Be certain you understand the pros and cons before making a choice.

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About Bob Campbell

Bob Campbell is a writer for Concealed Carry Magazine with a degree in criminal justice. Bob has been a firearms writer for decades, writing for Concealed Carry Handguns, Gun Tests, American Gunsmith, SWAT Magazine, Law and Order and Black Belt, among others. He has written 15 books primarily focused on handguns and training, including The Accurate Handgun from Gun Digest. In addition to serving as a peace officer and firearms instructor, he has also written curriculum at the university level.