action only. Production subvariants Colt Aircrewman The Colt M13 Aircrewman was an ultra-lightweight version of the Detective Special constructed of aluminum alloy, and made from 1951–1957 for use by US Air Force aircrews. They are distinguished by the Air Force medallion in the place of the Colt medallion on the checkered wooden grips, as well as a cylinder made of aluminum alloy. Within two years of issuance, reports of cylinder and/or frame failure began to plague the Aircrewman and its Smith & Wesson counterpart, the Smith & Wesson Model 12, despite issuing a dedicated low-pressure .38 Special military cartridge, the Caliber .38 Ball, M41 round. However, the cylinder fractures continued, and the weapons were eventually withdrawn from service. Colt Courier The Courier was produced in .22 Long Rifle, 32 Colt NP, 32 S&W long and short. Frame and cylinder are constructed of lightweight aluminum alloy. It was made from 1954 to 1956. Approximately 3,000 were produced in the two years. Colt Agent The Colt Agent was another model similar to the Cobra. The original Agents were very well made, with high polished finishes and highly checkered walnut grips. The bottom of the Agent grips was slightly shorter than that of the Cobra. The original Agent weighed 14 ounces and was available only in .38 Special caliber, with a 2-inch barrel and blued finish. It was made from 1955 to 1979. The original Agents had a smaller grip frame from the Cobra which made for a deeper concealment and the grip frame was later changed to match the Cobra in the late 60s. A slightly revised version of the Agent was released in 1973 with a shrouded ejector rod, with a weight of 16 ounces. In 1982, the Agent was briefly revived by Colt, this time with a parkerized finish; production continued until 1986, which made the Agent a much cheaper version of the Cobra. Colt Viper The Viper was essentially a 4" barrel version of the alloy-framed Colt Cobra in .38 Special. Introduced in 1977 and only produced that year, the Viper did not sell as well as Colt expected and was discontinued. In recent years, owing to its limited production run, the Viper has become quite collectable. Examples in good condition fetch unusually high prices. Ammunition Some have recommended against the use of +P-rated .38 Special cartridges in aluminum-framed Colt revolvers, as the Cobra was designed well before the