MAKING OF A RIFLE

Evening Post, Volume CXIX, Issue 95, 23 April 1935, Page 16

MAKING OF A RIFLE

(From the "Hlfleman," official organ of; the 8.M.1t.C, London. Continued from last week.) Thn rifling' operation on a small-bore target tide barrel If a fascinating one and to persona who appreciate mechanical contrivances it Is particularly impressive. The-machines ate ■bum especially for the purpose, and .are designed to combine revolving motion with reciprocating motion In such a way as to give the desired spiral cut., With the reciprocating motion constant, a change in the 'speed -of revolution will produce a change In the spiral. " , . The rifling cutter is held In a holder known as a "rifling head," which. Is an intricate mechanism so designed as to slide! through the borel of the barrel and provide .a uniformly' rigid support for- the rifling cutter. The rifling head ii secured to a long hollow shank through which!'.the cutter oil is -fed to the cutter. The rifling, head is pulled through the barrel in Its spiral path with tho cutter protruding, the cutter being pushed out and supported by a small wedge .contained' within the head. At the end of the cutting • stroke a stop on the machine pushes the wedge from underneath the cutter and allows' the latter to recede into the head out of contact with the barrel during the return stroke of the spindle. At the i end of the return stroke the wedge is again pushed into place, thus forcing tho cutter again into its cutting position. The barrel is then indexed —that is/-turned into the next position—and the next spiral groove Is cut. Much attention Is paid to- the fit of the rifling head in the bore of the barrel: the head* are lapped into - the .bore to assure a snug fit. They must be glals hard and perfectly smooth. .The "hook" type cutter Is | precisely ground and stoned to obtain the correct width of groove and the correct shape. The operator Judges the performance of the nutter by the feel of the -extremely thin ribbon of steel which is removed with each cutting stroke of the machine. Gauges are applied during the cutting to determine the depth and width of the groove. The diameter of rifling-Is .22251n and the twist Is one turn in 16in, with, six grooves .06651n In width. The width of land .13 ~0454 in. These dimensions are. the result of accurate calculation, supplemented' by exhaustive practical tests over a period of years. Here again you will find mechanics of long service and experience assigned to the rifling of the target rifio barrel. . CHAMBERING. The machining of the chamber to provide a seat for the cartridge in the breech end of the barrel is extremely important. The surface must be absolutely smooth and exact In size. Smoothness is necessary so that the fired shell may be readily withdrawn by the extractors. The size and shape of the chamber must be exact in order to provide suitable support for the metal shell at all points. Kough chambering is done by machines of special design using high-grade lard oil as a cutting' refrigerant. Due to. the exact requirements the final chambering Is done by hand. The men asslgnedj to this work are selected as especially fitted for it. They must produce in each barrel a chamber which is smooth and of exact dimensions «nd shape. There is no tolerance allowed. LEADING. The leading operation i 3 a type of lapping with fine emery and oil. The parrel is held upright with a rod through the bore and hot lead is poured into the muzzle end,' formIng a lead cast on the end of the rod of about seven Inches in length and of the exact shape of the Inner surface of the barrel. The barrel Is placed in a holder on a leadIng machine, which Is similar to a rifling machine, and the rod, with Its lead cast, Is secured to the spindle. The lead cast Is moved back and forth in a spiral path through' the bore and the operator charges it at each stroke with fine emery nnd oil;* This smoothes out the surface of the bore and diverts all of the minute reamer marks to the spiral path which the bullet takes when the mm Is fired. Experience has shown that lending is a very Important operation in the control of accuracy In shooting. THE LEAD TEST. In addition to a rigid gauge inspection of bore and rifling, the barrels are given a lead teat from breech to muzzle. A small lead slug is forced into the bore and upset so as to completely nil the bore in the same wanner as will the lend bullet. Tho lend Slug is then pushed slowly by hand from breech to muzzle *nd from muzzle to breech several times. By the feel of the drag on tho slug the Inspector is able to detect the minutest variation Wi the bore or In the rifling, with respect to either size nr surface. In our'opinion such'a test is the most Bevere nno to which the Interior of a barrel can be subjected. Defects can be discovered by this test which are not discernible by the use