GB789861A - Improvements in method of forming gun barrels - Google Patents

Abstract

789,861. Making gun barrels; forging. CANADIAN INGERSOLL-RAND CO., Ltd. June 1, 1956 [Sept. 14, 1955], No. 17061/56. Classes 83 (2) and 83 (4). In a method of making gun barrels a cylindrical member 14, Fig. 1, with an oversize bore 10 and counterbore 12 is progressively coldswaged over a mandrel having a portion 18 which forms the cartridge chamber and a portion 18a which forms a part of the bore. The member 14 may be initially reduced in diameter over the bore portion 22 by grinding or cutting so that only the portion x in the region of the cartridge chamber is oversize for the swaging operation and the bore portion cannot be inadvertently swaged. For subsequent forming of the bore portion over a mandrel 20, Fig. 3, the cartridge chamber portion is ground down to smaller size so that only the rifled portion 22 is swaged. A tapered lead for the rifling may be obtained by having the mandrel 18a slightly oversize and by leaving a portion y, Fig. 3, of the barrel unreduced by grinding so that a short portion of the rifled bore in the region of the shoulders 19, 21 is not swaged in the second swaging operation. The mandrel 18, 18a is supported on a piston-rod 14 subjected to hydraulic pressure in a cylinder 32 (not shown), which forces the mandrel against the shoulders 19, 21 to prevent it being forced outwards by the swaging of the dies 24. At the end of the swaging operation the cylinder is reversed to withdraw the mandrel. The mandrel 20 for the rifled bore is mounted on the end of a pistonrod 72, Fig. 9, which is progressively moved under the dies 24 by an hydraulic cylinder 50. The rod 72 is rotatably held in position in a fixed plate 76 by a thrust bearing 74. In a modification a separate rifling mandrel may be attached by a spigot to the end of the cartridge chamber mandrel 18, 18a and is separated therefrom as the barrel moves through the swaging dies.