Back to Basics Part 1 Moon Clips

Posted by George on 23rd Sep 2016

Back to Basics
The Revolver Supply Company started business in September 2010, 6 years ago this month; to provide supplies for the revolver shooters. Back then, there wasn't an easy way to find resources and supplies for competitive revolver shooting. We love shooting and competing with revolvers and from all the positive feedback we've received, it seems our customers think we are on the right track!
We've grown, done well, and swerved off track in a couple of areas (which is expected). I want to take some time to take you back to basics, and see if you're overlooking anything.

At the Firing Line:
You chamber your moon clip, close the cylinder, aim, pull the trigger, the revolver goes BANG, and hopefully hits fairly close to the area you were aiming towards. That's how simple it should be. Of course, I'm leaving out all the safety concerns, practicing hours, reloading time, the hot sun (or rain) that is beating down on you, and the money and time you've invested into all of this; and that is the point of this WHOLE newsletter! Let's go over the basics and see if you are doing all that you can to get the most fun out of our sport!

Moon Clips:
Moon Clips are by far the most popular method for reloading a revolver. Of course there are other methods including: speed loaders, speed strips, and even one round at a time. Most importantly the revolver has to be designed to work with moon clips, and it has to have the correct moon clip to work well! Starting with the S&W Model 1917 revolver, made for the war effort (WWI). It has a design controlled by the government and is the best example of how a moon clip combined with any in spec. brass does work well in these revolvers. That revolver became very popular after WWII which lead us right into the 1970s where this sport began to gain popularity; target matches and of course bowling pin matches were big events.

45 ACP 6 Shot
The 6 Shot revolver that uses the 45 ACP round is just as simple and straight forward as it gets. The cartridge goes into the cylinder and head spaces (stops) on the case mouth. So you can chamber a round, fire it, pick it out with your finger nails, and that system as we all know can be very accurate. The moon clip is just a helper/holder for loading up 6 rounds and extracting those rounds which can be done quite fast. Every so often we get a call about some strange brass (no name discount) that won't work with moon clips. But that is a very rare occurrence. (Wish they were all like this!)

627 357 8 Shot
From the factory the next revolver that we came across was the 627 8 Shot chambered in 357. Originally, 357 cylinders were not designed to use moon clips. After gunsmiths invented the method for adding moon clips to 38/357 revolvers the S&W factory cut the cylinder to make a space for the moon clips. The moon clip held the rounds using the groove that was cut into the brass next to the rim. This groove however, is not part of the SAAMI cartridge specification and be any size and changed at any time. Also, remember that the 38/357 round head spaces on the case rim. As you are probably aware Winchester Brass has the thinnest groove and works best with moon clips that are: 0.020" or 0.022" thick. Remington, Federal, and most others like an 0.025" thick moon clip. Starline Brass even likes thicker moon clip. Keeping in mind, faster reloads come from a tighter moon clip assembly. And now, in a case such as this, you have to be BRASS SPECIFIC unlike the 45ACP. You have to sort your 38/357 brass and match to different thicknesses of moon clips.

Other cartridges and revolver combinations were manufactured like the 40 S&W, 10MM, 38 Super, 32 H&R Mag, and 22 Long Rifle, to name a few. Many of those are still very popular.

9 MM
And FINALLY!! This brings us to the newest revolvers chambered for the 9MM cartridge. The 9MM (9x19) is a very old design and is used world wide. When putting 9MM cartridges into moon clips several new problems show up. The moon clip grips the cartridge using the extractor groove. The groove has a dimension of 0.347" +0.00 / -0.020". If we made a moon clip to fit the maximum dimensions, then the minimum dimensions cartridges would fall out, and vise versa. So, NO one moon clip design can fit in all 9MM cases that are made to meet the specification. We choose to make moon clips to serve the upper end on the tolerance range and that is why some rounds fall out. You have to sort your 9MM brass.

Next consider head space. 9MM cartridges head space on the case mouth (just like the 45ACP). The dimension from the case mouth to the back of the case is 0.754" +0/-0.010" and the case is tapered. So, as the case length grows from repeated firing and resizing, you must check that the overall length does not interfere with the rear of the case to the revolver frame dimension.

We all have a lot to learn with the 9MM rounds in the revolvers, and predict that some day there will be 9MMR (revolver) cases.