School me on .22 Conversion Units please.

[ap3572001]

I have a clean Series 70 Cov't model made in 1975. I would like to have a Colt .22 conversion unit correct for the gun . ( Made at in about the same era). Also school me on the diferent conversion units made by colt.
Which one would You get?

[kenhwind]

Any of the post war Colt Conversion Units with the Accro Sight (Similar to Gold Cup & same as Colt revolvers) could be considered correct for your gun. But the earlier Units did not include a barrel bushing, whereas the ones made in the 1970s did because the MKIV Collet Bushing was not compatible with the Conversion Unit barrel.
As for differences, I know what they are, but will let someone with a little more insight and data describe them.

If I could find a round top Colt Conversion that wasn't over-priced I would buy it.

[tmd17]

...If I could find a round top Colt Conversion that wasn't over-priced I would buy it.

They are out there, you just have to be vigilant. I have two of the conversion units, but I don't know enough about them to educate any one. I love mine, and both function flawlessly!

[kenhwind]

I had a Colt ACE and it would shoot until is was too dirty to operate. But I sold it, and have since nominated myself for the "Donkeyhead award".

[ClintB]

I'm also considering a conversion kit.

I've got a series 80 stainless enhanced government model. Is there a version of conversion specific to that model?

[ace]

well this isn't wts, but for any of you guys interested, i have several colt factory 22 conversion units in original boxes from new to near new condition. 70 and 80 series. i had some posted in wts about a year ago, i also have some others that i never listed there. you can pm me or maybe even ask me here if you need info on them you're interested.

[JudgeColt]

ace, I am interested in your "70 series" Conversion Units. I thought I had all of the variations, but have never seen nor heard of a Series 70 Conversion Unit. Please picture the Series 70 Conversion Units and their box end labels. We can discuss price by private message once I see your Series 70 Conversion Units.

I am also interested in your Series 80 Units. The end labels vary on Series 80 Units from what I have seen. Please picture your Series 80 box end labels and box styles.

[JudgeColt]

Is there a version of conversion specific to that model?

There is a Series 80 Conversion Unit that must be used with any Series 80 pistol with the firing pin safety still installed. Unfortunately, Colt never made the Units in stainless.

The Ace II Conversion Unit will also work with a Series 80 pistol, but it has an alloy slide, and the main spring housing is supposed to be changed to use the conversion. (Apparently, most Ace II Units will work without changing the main spring housing.)

[JudgeColt]

Also school me on the diferent conversion units made by colt.Which one would You get?

I will try to teach you what I know about Conversions. It is a work in progress and I am always interested in learning about variations I do not have, such as the Series 70 ace mentions above. If anyone sees anything incorrect, please tell me what is incorrect.

Based on my own collection and research, I have tried to summarize the chronology of Conversion Units and their boxes. Here is what I think is a fairly accurate chronology and box style summary of Colt rimfire Conversion Units for the Model O, and ending with a couple of related centerfire Conversion Units for completeness.

The Service Model Conversion Unit, using the floating chamber designed by "Carbine" Williams, was introduced in 1937, and these early Pre-War units were serial-numbered with a “U” prefix on the serial number. These units use the Stevens rear sight. A few serial-numbered Conversion Units were made Post-War. The serial numbers began a U1 in 1938 and ended at U2670 in 1946. There were gaps in the numbering so there were not 2,670 serial-numbered Conversion Units made.

The serial-numbered units were shipped in a small black hinged-lid box with labels on the top of the lid and the end of the box stating “.22-.45 Service Model Conversion Unit” with (Floating Chamber) centered in a second line on the label on the top of the lid. The very first units used a smaller box with one less row of interior partitions than the later boxes. The inside of the lid contains the serial number written in pencil along the left side of the lid. The black printing inside the lid identifies the eight components of the unit.

Early Post-War non-serial numbered Conversion Units also use the Stevens rear sight. Early Post-War, the ejector style was changed from a machined part to a twisted, stamped part. These early Post-War units used a partitioned Pre-War style black hinged-lid box with a top label and an end label that both state “.22 Service Model Conversion Unit” with (Floating Chamber) centered in a second line on the label on the top of the lid. Only seven components are listed inside the lid in black ink, with the barrel bushing being omitted and only the recoil spring itself being mentioned, instead of the recoil spring, guide and plug being mentioned as one component on the eight-component parts list.

Probably in 1948, the covering on the box was changed to a dark brown leatherette texture, and the top label was dull gold with green lettering stating “Colt” with “.22 Conversion Unit” centered in a second line. The seven components are still listed inside the lid, but in brown ink. The partitioned interior is buff-colored. There is no end label on my example. This style of box seems to be the rarest. It was probably phased out in 1950 or so, when the larger medium brown leather grain hinged-lid box with the dark green enameled-paper interior was introduced. This box has a fairly large Rampant Colt in the top center of the lid and a dull gold end label with green lettering stating “.22 Conversion Unit.”

Probably in 1948, the rear sight was changed to the Coltmaster. In about 1952 or 1953, the rear sight was changed to the Accro rear sight, which continued through the end of production in the early 1980s. Elliason rear sights were said to be factory-installed on some late units, but I am skeptical.

Probably in 1955, the box style was changed to the two-piece, telescoping-lid box with the wood grain covering and dark green interior. There are no partitions in this style of box. The Conversion Unit box styles generally followed the box styles for guns of the same vintage, with the wood grain lid and black bottom box style coming next in line. I have never seen a Conversion Unit box with the dirty yellow interior and wood grain exterior of the late 1960s and early 1970s, but there may be such a box. The next box style was the wood grain sleeve with the Styrofoam-insert interior and gold foil end label with brown lettering, which was used through the end of production. The instruction sheets in the Post-War units are usually date-coded, but not always. It is not uncommon to find earlier date instruction sheets shipped with later units, so the literature date code is not always reliable.

A rare variation is the fixed-sight, round-top version using the model number O3151, which was shipped late in the Pre-Series 80 production period in a wood grain sleeve, Styrofoam-insert box, but with a handwritten label. Some examples have only the model number and some other codes in the upper left and right corners of the end label, but no reference at all to the contents of the box. Others have “Conversion Unit” handwritten on the end label.

When the Series 80 guns were introduced in 1983 with the firing pin safety, a new Series 80 Conversion Unit was introduced, also using the floating chamber, but very few were made, and are rare today. These were shipped in a natural cardboard hinged-lid box with a very sharp, large rubber stamp imprint on the end label identifying the contents. I have seen some Series 80 units with hand-written labels, which the owners claimed were original. These have a “FS” suffix on the model number on the end label, signifying “Firing-Pin Safety.”

The last Colt conversion unit is the Ace II Conversion Unit, introduced in about 1988 and discontinued in about 1999, when Colt discontinued all revolvers except the Python and all automatic pistols except the Model O. The Ace II uses an aluminum slide and reduced power main spring housing, as well as a different magazine. These were shipped in a tan or blue plastic hinged-lid box with foam liner.

Rear sights as outlined are a good basic clue as to age. Another clue is the slide serrations, which I believe changed from vertical to slanted in the mid-1960s, but I am not sure of that date. The operating name of Colt changed to “Colt’s Manufacturing Company” in 1948, and then changed back to “Colt’s Fire Arms Manufacturing Company” again in 1955. The manufacturer’s name in use when the unit was made will be stamped on the slide so the name is a great clue for units made in the late 1940s and 1950s. Box styles as outlined can be a great clue to age, but I have seen many Conversion Units for sale in the wrong boxes so the box style cannot always be relied upon.

While not a rimfire Conversion Unit, in the interests of completeness, Colt also made a Conversion Unit to convert the .22LR Service Model Ace pistol to .45ACP. Colt only made 112 of these units beginning in 1938 at serial number U1 and ending in 1941 at U112. These rare units were shipped in a partitioned small black hinged-lid box with a label on the top of the lid stating “Colt” centered over a second line stating “.45-.22 Government Model Conversion Unit,” which was in turn centered over a third line stating, “For use with the Service Model Ace Only.” The inside of the lid contains the serial number written in pencil along the left side of the lid. The black printing inside the lid identifies the six components of the unit.

While not a rimfire Conversion Unit either, Colt also made a 9mm Conversion Unit in the 1980s. My example has a handwritten end label. The caliber is shown as "9 m/m." The model number is O3009. Unusual is the fact that there is a rubber stamp, a bit smeared, stating "H 8 21," stamped diagonally just above the "S/N" on the label. Another interesting thing about this unit is that the box is big enough for an 8-inch gun, rather than being the apparent 5-inch length of other Styrofoam-insert Conversion Unit boxes. The 9mm Conversion Unit is a Series 80 with a firing pin lock. The rumor was that Colt offered to convert all Models of 1911/911A1 in the military inventory to 9mm to satisfy the desire to have a NATO standard handgun cartridge. Nothing ever came of it, but apparently Colt decided that it would be wise to offer a 9mm Conversion Unit during the "Wonder Nine" era and created this conversion. I think these are rare.

Hope this helps to understand the long, varied and interesting history of Colt Conveersion Units. You will have to decide which one is best for you.

[T.May]

Judge...thanks for the education!!!!