- As the US prepared to enter World War I, it lacked the capability to manufacture enough of the newly adopted
M1911 pistol. In 1916, someone at Smith & Wesson figured out that the rimless .45 ACP cartridge could be made to function
reasonably in the firm's large-frame revolver by inserting three of the rounds in a stamped-steel half-moon clip.
The Army adopted that revolver as an expedient and Colt created a similar one on their large frame. This resulted in the
rare case of two mechanically distinct handguns sharing the same designation - M1917.
- The three-round half-moon clip was so named as it had a semicircular shape, with the cartridges inserted from the
"inside." The concept was not all that popular with early Border Patrol agents who were issued M1917 revolvers and M1917
rifles - another expedient to deal with the inability to produce enough of the relatively new M1903 Springfield. Then
came the sport of timed bowling-pin matches and someone started making full-moon clips that revolver competitors
felt gave them a faster reload with the rimless .45 ACP round than using a speedloader with rimmed cartridges. The
full-moon clips - generally referred to simply as moon clips today - have a star shape, with an opening for the center of
the extractor star - and cartridges inserted from the "outside."
- Today, revolvers are made to handle such pistol calibers as .380 ACP, 9x19mm, .40 S&W, 10mm and .45 ACP with the use of
moon clips. Because some shooters value what they believe is a faster reload with a moon clip, some .38/357 revolvers are
manufactured to allow their use and others - typically in other chamberings - are so modified. These work by
cutting a recess in the center of the rear of the cylinder, to accommodate the moon clip while leaving enough of the
outer contour for the rim of the case to headspace, whether or not the clip is used. Unlike with the rimless
pistol cartridges, the rimmed revolver cases will also extract with the extractor star without the use of the clips.
- Moon clips are susceptible to bending and breaking - the latter particularly with the relatively flimsy clips used for
five-shot 9x19mm and .38/.357 revolvers. Bent clips - just enough to keep them from lying flat - may not only slow the
claimed faster reload, they may also absorb some of the energy of the hammer strike, hindering reliable ignition of the
primer. In the worst-case scenario, they may even hinder rotation of the cylinder. An additional issue with moon clips
for revolver cartridges is whether their thickness matches the brand of ammunition that you intend to use.
- Around the 1980's, French police used revolvers chambered in 9x19mm, both with and without moon clips. (Smith & Wesson's
Model 547 was specifically designed to extract that rimless case without the use of moon clips for such a contract.) It
is worth noting that those French units who continue using revolvers - typically SWAT-style entry teams - have
transitioned to France's own Manurhin .357 Magnum revolvers.
- If you've got the spare funds, I have no objection to seeking out an out-of-production S&W Model 547 or a currently
produced Charter Arms Pitbull revolver, for the expedient use of 9x19mm ammo when it is more readily available than
the traditional, rimmed revolver rounds. Dependence on moon clips, however, negates one advantage of the revolver - the
ability to keep loading with loose rounds when magazines, clips, speedloaders and similar devices are not available.
Double-action revolvers generally function more reliably with the rimmed cartridges around which they were designed.
Those concerned with saving a second or two in reloading time may be better served by a so-called "New York reload" -
transitioning to a second revolver.