Repairing the Colt Service Model Ace/Conversion Unit Magazine

The Series-70 Colt Service Model Ace is a Government Model Pistol that resembles the Gold Cup in profile, but is chambered for the .22 Long Rifle cartridge. The Service Model traces its beginnings back to the late 1930s, and is actually nothing more than the .22 conversion unit installed on a Government Model .45 receiver, and marketed as a separate model. The original Colt ACE was a straight blowback design that proved to function unreliably.

This problem was overcome by David Williams, who designed the floating chamber that provided enough momentum to operate the lightened but still big slide of the GM pistol. Williams would later become famous for his association with the development of the U. S. M- 1 Carbine. The Ace Magazine Having purchased a Colt Service Model Ace .22 Long Rifle semi-automatic pistol, it was only natural to purchase an extra magazine.

These magazines have removable floorplates, recessed sides, magazine body fillers, and a steep price tag. Decent Government Model mags sell new for between $20 and $30. When I purchased my spare Colt ACE magazine, they sold for about $40, but new Colt ACE or conversion-unit magazines now sell for as much as $65. 22 pistol is essentially a Colt .22 LR conversion unit assembled on a Government Model frame.

These magazines can be completely disassembled, and consist of a removable floor plate, floor-plate retainer, the body, a body filler, spring, spring base, follower, and follower stud. The cartridge followers on these magazines are made of a black synthetic

plastic’probably nylon. The Colt factory mags are very nice and work quite well. Failure to Lock the Slide Open With the low cost of .22 LR ammunition, I put a lot of rounds through my Service Model Pistol. The way the magazines are made, the follower projection that engages the slide stop can rub on the mag body. I don’t know if this caused one of my magazines to fail or not, but eventually the follower failed to lock open the slide after the last shot.

I like to have a spare magazine for a semi-automatic pistol, and prefer two. Now what was I to do with a magazine that would cost $65 to replace because it needed a 75-cent part. I tried an aftermarket magazine The left follower is the one that was repaired and the hole for the machine screw can be seen. On the far left is the modified screw insert. The right follower is in original condition. that was not up to standard. Although it worked reasonably well, the feel and finish just weren’t there.

The only good solution to the problem was to fix that Colt magazine. A Permanent Fix At first I thought about making an aluminum follower or trying some epoxy to fix the very small area. But then I came up with a better idea. Why not install a screw into the magazine follower, and fix it for good? After I convinced myself that this would work, I found a 4-48 slotted fillisterhead machine screw (an old revolver grip screw) that should do the job. I disassembled the magazine and put the follower in a small vise.

With a rotary tool, I cut into the follower just enough to drill a hole into it. Then I carefully drilled a #42 hole in the follower, being certain that the screw slot would be even with or higher than the ledge that activates the slide stop. The next step was to tap the hole. After tapping the hole, I inserted the screw and used the rotary tool to relieve enough plastic for the screwhead to fit, and screwed the screw into the follower until the slot was level.

Since the screw projected out the other side, it had to be shortened. I marked which side of the screwhead was up, removed the screw, and with the Dremel cut-off disk I cut off that half of the screw head. When cutting off the screw head, I cut into the screw body and made a small slot for a small screwdriver. Finally, I reinstalled the screw and then shaped the remaining part of the screw head to blend into the leftover portion of the original follower projection.

At first the flat surface was a bit too high so I continued trimming until it worked perfectly. Conclusions This took a little while to do the first time, but it was a whole lot cheaper than anew magazine. And besides, this one is fixed; if I’d bought anew magazine, it would eventually have suffered from the same problem. With a steel insert in that plastic magazine follower there should be no worries about repairing it again. One of these days I’ll repair my other magazines.

At least the next time, I can spend more time doing and less time thinking and planning. I