Some of the more interesting Colt products, both from the collector’s and shooter’s perspective, are those in the "Ace" line of .22 rim-fire pistols, based on the Government Model .45. Included in this group are the original Ace pistol of the early ’30’s, the Service Model Ace introduced just before WWII, and the .22-.45 Conversion Unit, which allowed the owner of a Government Model to practice with cheap .22 ammo while retaining the feel of the big pistol.

The first Ace was a conventional blow-back operated semi-automatic that outwardly resembled the gun adopted by Uncle Sam in 1911, but with the swinging link and locking lugs of the .45 replaced by a barrel pinned solidly into the frame by the slide stop. Other modifications included a 1/4" shorter slide and barrel, a unique rim-fire firing pin and stop, ejector, and a stack of shock-absorbing washers under the barrel. These washers limited slide travel, necessitating relocation of the slide stop notch to suit the new .22-length action. Atop the slide sat the adjustable Ace sight, also unique to this model. This sight was developed at the behest of the U.S. Army, which was helping in the development of the Ace, and upon whose approval Colt depended for the promise of volume sales.

Reports on the gun, both contemporary and modern, are a mixed bag. The pistol was beautifully fitted and finished in the manner of all pre-war Colts; and accuracy, from what amounted to a fixed-barrel pistol, was excellent. Of course, the Ace had the familiar feel of the .45, but there were problems associated with trying to operate a big-bore size pistol with the recoil energy contained in the .22 Long Rifle cartridge. With Colt’s own sleek, handy Woodsman on the market, the Ace’s popularity was never great, with either the commercial or military contingent; but the gun remained in production for about ten years.

Still, there was interest in a gun with the handling characteristics of the G.I. .45, but with the economy of rim-fire ammunition. In the days before hand loading was widespread and commercially reloaded ammo was available, the cost savings to the dedicated shooter was considerable. There was evidence, though that the rim-fire ammo of the day was a contributor to the Ace’s reliability shortcomings, the pressures generated not being as consistent as today’s uniformly excellent products.

Colt went back to the drawing board, to find a better way to adapt the small cartridge to the big pistol. If the pistol couldn’t be made to act small, maybe the cartridge could be made to act big. Enter David Marshall "Carbine" Williams, whose expertise in perfecting the short-stroke gas piston system would earn him his nickname after his design was incorporated into the mechanism of the wildly successful Ml Carbine. A variation of Williams’ principle, in which a separate "floating" chamber was itself the piston, allowed the recoil energy of the .22 cartridge to be boosted sufficiently to cycle a slightly modified .45 slide. Although this new Ace would still have many unique parts, it was very much more like the service pistol than the original one, so it would be called the Service Model Ace. It not only looked and operated almost identically to the .45, its new recoil-boosting design made it an even better trainer, causing Colt to tout it as an ideal companion to their new National Match .45. The Service Ace even included the new Stevens-pattern target sight as offered on the center-fire pistol.

The development of the Service Ace, with its fewer unique parts, allowed Colt to market a "conversion" kit of components that permitted someone already in possession of a Colt Government Model, National Match, or Super Match to swap the slide, barrel, spring and magazine for those in the kit, and have a .22 pistol. Conceptually, this was an even better idea than the Ace, as the .22-.45 Conversion Unit allowed retention of the all-important feel of the trigger of the parent arm. And since economy was the whole point of the exercise in the first place, having to buy only half a gun was an added attraction. The same idea, in reverse, did not work out so well, as the .45-.22 Conversion was a short-lived offering from Colt (In what has always seemed a confusing circumstance, Colt chose to name the Conversions in what would seem to be a counter- intuitive manner – the one converting the .45 to a .22 being the .22-.45 Conversion. If you take the meaning to be "a .22 from a .45", it then makes sense). A few years after the introduction of the Service Ace and Conversion Units, the world was plunged into war, and all of Colt’s Aces were drafted into military service for the duration.

In 1949 the original Ace and Service Ace were no longer available, the last pistols having been assembled from parts produced during the war. The .22-.45 Conversion Unit however, was reintroduced to the commercial market, in slightly simplified form, and sporting a new rear sight – the Coltmaster. At that time, Colt ceased the serial numbering of the units, continuing to sell and catalog them throughout the 1950’s and ’60’s, although they were not always in production.

In the late 1970’s, Colt reintroduced the Service Ace pistol, updated with, you guessed it, a new rear sight. The Accro was pressed into service (pinned, actually . . .), this sight having superseded the Coltmaster in 1955.

Although there were detail changes made throughout the production runs of all of these models, I emphasize the rear sights as an aid to identifying the era in which a given pistol or conversion was built. It’s possible to date pieces by checking serial numbers against various lists intended for just that purpose, but if the subject is an unserialed conversion, or just a rough estimate of age is desired (is it pre- or post- war?), then the rear sight tells a lot.

The Ace sight was fitted exclusively to the original Ace pistol, from 1931 to 1941. It was screw adjustable for windage and elevation, and was only slightly bulkier than the fixed sights available today on Colt’s service pistols. The production runs of the Ace and Service Ace overlapped for about four years, the latter pistol being commercially offered initially in 1937. By this time, Colt had adopted the Stevens sight for its other target arms, so the same sight went on the Service Ace, and the Conversion Unit when it was introduced in 1938. This sight featured a "shield" type rear blade, presenting a flat, square surface, angled to prevent glare. Its chief improvement over the Ace sight was the slight lengthening of the sight radius that it allowed. When the Conversion Unit was reintroduced after the war, it was equipped with the then-new Coltmaster sight, which was also on Colt’s other adjustable-sighted models, from the Match Target Woodsman to the Officer’s Model Special. The Coltmaster was similar to the Stevens in general configuration, but featured a single, spring-loaded adjusting screw for elevation, and one for deflection, dispensing with the locking screws of the earlier design. The blade showed the notch set into an angled, horseshoe-shaped cut-out in a rounded, oppositely-angled surface – the whole sight picture looking very much like that of the "modern", highly touted Novak fixed sight. In 1955 the Accro replaced the Coltmaster throughout Colt’s line. Whereas the earlier sights had all been set into transverse dovetails, the Accro was held in a lengthwise slot, in a rib raised above the slide. When the Service Ace was reintroduced after a 20-year absence from the market the Accro was, and still is, the standard on most Colt models. This sight features a thin blade, set into a heavy body containing the adjusting mechanism, similar to that of the old Micro and Ruger sights. A shooter who teams his modern Ace or Conversion Unit with a Gold Cup National Match might want to switch the Accro for the Colt-Elliason sight which is a drop-in modification, and commonizes the sight pictures.

All of the Aces and conversions were finished in the blue of the day, with the pre-war models in overall polished finish, and the later models done in the polished flats/sandblasted rounds, which is still in use at Colt. Military surplus pieces can also be found parkerized, and a magazine photo of a "rare" nickel-plated Conversion Unit would indicate that some were also finished in that manner at the factory.

If you are a shooter, and you have a Service Ace or Conversion Unit, you are fortunate, because they have never been made in large numbers, having been rendered less viable market-wise by hand loading for the center-fire calibers and the introduction of newer, cheaper conversions by other manufacturers. Although the original Ace pistols are almost too valuable for the collector to shoot, with prices well into four figures for pristine examples, most Service Ace and Conversion Units can be shot; but not necessarily with much accuracy or dependability. Published reports indicate great variations in accuracy, and everything from feeding and ejecting woes, to severe bore leading. While the Service Ace can be a well-fitted gun, the Conversion Unit’s potential for accuracy is limited by the nature of its one-size-fits-all concept, and reliability varies from piece to piece. Williams’ ingenious "vibrating member", the floating chamber, seems to be the source of most of the grief, while acknowledging that the gun wouldn’t operate at all without it.

My own Conversion Unit is a circa 1950 model, with the Coltmaster sight, and without serial number. The post-war Units were not supplied with a barrel bushing, recoil spring guide or plug, as were the earlier ones; and the whole is packaged in a black cardboard box. I have also seen conversions of the same period packed in brown boxes. The slide shows the legend COLT’S MFG. CO. HARTFORD, CONN. USA which was peculiar to products manufactured in the 1947-55 period – a handy way to recognize Colt products from that era.

Mounted on an M1911Al lower, many trips to the range, over a period of years, ended in as few as fifty round fired, with the floating chamber no longer floating in its seat in the barrel. So caked with lead and powder residue that it had to be pounded out with a mallet, the separate chamber worked much better in theory than in actual use. Hundreds of rounds of Remington, Winchester, CCI and every hardware store brand I could find were sent down range – but rarely more than fifty at a time, lest the tightly-fitted chamber would freeze up. Besides the choking, the converted .45 showed indifferent accuracy. Although the donor pistol is a nice, low-mileage Colt (purchased by my father through the NRA in the ’50’s for $20!), the Conversion Unit was designed to fit every pistol made since 1911, and tolerances are necessarily large. To improve the grouping, all of the conventional work done in "accurizing" a .45 can be applied – closely fitting the rails, installation of a National Match bushing, etc. But could this tightening rob the slide of the necessary energy to reciprocate under the urging of the diminutive rim-fire? Even if the accuracy could be improved, what fun is a pistol that can only go fifty rounds? Old, printed road-tests of the Service Ace and Conversion Unit advise against using standard velocity ammo, as poor function and leading would result. I was getting plenty of leading from high velocity stuff, so I thought to go one better, and try "hyper-velocity" ammunition (Since virtually all .22 ammunition on the market today is "high velocity", then why isn’t our choice either standard or low?). These cartridges feature lighter bullets, driven faster than even high velocity ammo. The difference was like night and day. The hyper-velocity CCI Stingers left only a light wash of lead build-up, even after 100 rounds. Rim-fires of all types seem to display pronounced preferences for some types or brands of ammo over others, and now that I have discovered the improved function of the hyper-velocity ammunition, I can investigate the accuracy potential of other brands, as well.

Why does the ammunition so dramatically affect the operation of this gun? Putting my liberal arts education to work on this problem of combined engineering and physics, I believed originally that the leading was caused by the bullet having to jump a gap between the chamber and the barrel as the gun fired, like the flash gap in a revolver, only internal. I reasoned that the high velocity bullets were able to pass the chamber/barrel joint before the chamber moved under recoil! Yeah, that’s it! But, then I remembered from my "Physics for Liberal Arts Majors" class, that part about the equal and opposite reaction, and figured that the action of the gun would open just that much faster as well – and the bullet would be long gone before the recoil could overcome the inertia of the slide, and the force of the recoil and mainsprings. After additional thought, and examination of a dozen different bullets, it appears that the bullets of the hyper-velocity rounds have a much thicker jacket, compared to the plated bullets of the slower-moving ones. This allows the bullets to pass the joint of the chamber and barrel (while it’s still tightly closed!) without shaving or distortion, resulting in cleaner shooting. Also, it has been reported in various publications that a coating of this, or a drop of that special lubricant will prevent leading of the chamber. I have not found this to be the case, so working to reduce the leading to a minimum is the way to go.

Although the days of the Aces as serious sub-caliber trainers are mostly over, they do afford a moderately-priced collectable, and the economical shooting originally promised 65 years ago.

 Bibliography:

(Although there are no direct quotes from any of these sources, I referred to all of them to varying degrees.)

Colt: An American Legend
R. L. Wilson
Abbeville Publ., 1985

A History of the Colt Revolver
C. Haven & F. Belden Bonanza, 1940

Guns & Ammo Magazine:
1/76, 10/77, 9/78, 12/80, 10/83, 8/86