Bendix ¡5-mm Machine Gun. The first attempt to meet the characteristics for the caliber .60 aircraft machine gun was to modify a 20-mm Hispano-Suiza automatic cannon. 1'he receiver was identical and parts of the gun were interchangeable with the 20-mm, Ml. The chicf difference was in the barrel, which was chambered for the 20-mm ease, bored and rifled for the 15-mm bullet and fixed in relation to the mount. The whole gun was rigidly mounted and the muzzle brake and recoil mechanism used on the 20-mm gun were eliminated.
Gun, Machine, Caliber .60 T17. In September 1942, a project was initiated to convert the 15-mm German aircraft gun, MG 151, a recoil-opcratcd, air-cooled, and belt-fed gun, to use the caliber .60 cartridge. In October 1942, Colt's Patent Fire Arms Manufacturing Co. undertook this conversion..
Figure 1-9. Gun, Machine, Caliber .60 T17E1.
The gun was designated Caliber .60 Machine Gun
T17. it was found necessary to rechamber the
barrel, lengthen the receiver, feed way, bolt, cam tube, and cover, and to make a few other minor design changes. New links were provided by the Autovre Co.
Gun, Machine, Caliber .60 TUFA. The Frigidaire division of the General Motors Corp., Dayton, Ohio, undertook in January 1943 to provide 10 pilot models of the aircraft machine gun, caliber .60 T17E1. The model was to be essentially the same as the T17, except that the rate of fire was to be increased to 800 rounds per minute and the high trunnion reactions were to be lowered by incorporating in the design a recoil adapter developed by the Edgcwater Steel Go. at the request of the ordnance officer at Wright Field. Links for the gun were developed by the Autoyre Co. of Oakville, Conn. Complete drawings of the T17 gun were prepared by Frigidaire and an engineering study was made to redesign the weapon for cheaper mass production.
Gun, Machine, Caliber .60 T17E2. The Frigidaire division was then asked to prepare two additional models which would use strengthened components and a barrel with a thicker walled chamber as the chamber had expanded during tests of earlier models. SAE 1060 steel was used in the T17E1 wherever possible. In the T17E2 this policy was abandoned and SAE 4640 steel was substituted. Fabrication of these models involved the use of sheet metal stampings and hydrogen brazing. T his gun was designated the T1 7 E2. In May 1943 the General Electric Co., Bridgeport, Conn., accepted a contract to develop an clcctric charger for the T17E2 gun. It appeared at this time that the most profitable development of this item would be a charger integral with the gun. Two T17E2 machine guns were delivered to Aberdeen Proving Ground for test on 25 August 1943. Each was equipped with manual charging and firing equipment and recoil adapters. Electrical charging and firing solenoid were provided as alternate components. One gun was fired 557 rounds. Ejection difficulties developed, but after modification of the ejector the gun functioned fairly satisfactorily with a rate of fire of 600 rounds per minute. T he second gun with the General Electric charging mechanism was fired 143 rounds. ' A combination gun was built from parts of guns No. 1 and 2 and fired 327 rounds at 658 rounds per minute and a maximum muzzle velocity of 3,696 feet per second. Numerous malfunctions were encountered which indicated that considerable further development work was needed.
Gun, Machine, Caliber .60 T17E3. Beginning in September 1943, attention was concentrated upon the manufacture of seven T17E3 guns with both percussion and clcctric ignition. On 15 December 1943 this order was increased to 10 guns. The electrical ignition mechanism was modeled upon that of the German 20-mm gun. A program was also initiated for the development of a bolt with the sear forward. It was expected that this, together with electrical ignition, would permit synchronization of the gun when cither electrical or percussion primed ammunition was used. On 16 November 1943 Frigidaire was requested to develop four auxiliary gun chargers to be used as a standby device in case of failure of the electric charger. Because of a requirement placcd with the Ordnance Department hv the Navv Bureau of Ordnance for delivery of 2,500 caliber .60 aircraft machine guns with auxiliaries and Sparc parts in 1944, limited procurement of the T17E3 was initiated 2 December 1943 and approved 16 December 1943. Rock Island Arsenal was commissioned to make these guns. This gun weighed 135 pounds, including rccoil mounting adapter, electrical charger and solenoid, and feed mechanism. The rate of fire was 600 rounds per
minute, and the muzzle velocity was 3,500 feet per second. The gun was 92 inches long and had a maximum trunnion reaction of 3.500 pounds. At the request of the Army Air Forces the original procurement was increased to 5,025 guns by Ordnance Committee action on 23 December 1943.
Gun, Machine, Caliber .60 777FA. Similar to the T17E3 with modification of the mechanism to use ammunition belted in a new link. Developed by Sanford Engineering Co.
Gun, Machine, Caliber .60 T17E5. Similar to the T17E3 with modification of locking lugs on bolt-licad and breech ring and change in design of locking and unlocking cams. Developed by the Frig-idaire division of General Motors .
Ilispano-Suiza Caliber .60 T1S Machine Gun. A second modification of the 20-mm Hispano-Suiza cannon was made by reehambering the barrel for caliber .60 case and boring and rifling for the caliber .60 bullet. Corresponding changes were made in the bolt and extractor. This gun was lircd a small number of rounds (not more than 50) automatically. Official designation of the gun was Caliber .60, T18. Since radical redesign of the Hispano-Suiza cannon appeared necessary if this gun was to meet aircraft requirements, work on this model was discontinued.
Gun, Machine, Caliber .60 T18EI. After approval by Headquarters ASF, it was recomended that further investigation of caliber .60 mechanisms
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