MAKING ARMY RIFLES.

New Zealand Herald, Volume LII, Issue 16050, 16 October 1915, Page 4 (Supplement)

MAKING ARMY RIFLES.

'I vik modern military rifle is modest enough in appearance, and at first sight would not give one the impression of requiring elaborate machinery and much skilled labour to produce it. But when we come to consider the powerful work that it has to accomplish and the accuracy it attains when used, we can. perhaps, realise to some extent the high quality of the material and the excellence of the workmanship that must be put into it. There are three great essentials in a good rifle; it must be accurate in shooting, of great wearing quality, and safe to use. It is quite necessary, then, that not only must the highest skill and most modern tools be used in its production, but that the metal and wooden parts shall be of the best available material. The quality of the steel used is of prime importance. Steel, as we all know, is an iron containing a small percentage of carbon. According to the amount of carbon contained in the steel, so it is possible to obtain a metal of various degrees of hardness or softness. "Mild carbon'' steel is that which contains carbon to an extent not greater than three parts in a thousand, and the high carbon ' variety contains carbon above the percentage indicated.' Up to a certain limit the greater the amount of carbon contained in a steel the More does it possess the property of hardening when it is subjected to certain treatment in heating and cooling. The Steel for the* Barrel. 1 he rifle barrel can be made of steel cf either of the varieties mentioned. The metal must, however, be of first-rate quality, able to withstand the high pressures (varying from about 16 tons per square inch at the breech end to four tons per square inch at the muzzle end) exerted by the gas evolved from the cartridge It has also to combat the erosive nature of these gales, which are of such an extremely high temperature that they would completely wash away the grooves of rifling of the barrel made of inferior steel. 'Ihe steel for the barrel is supplied in round bars of about a foot in length. These bars are subjected to forging or rolling, an operation which doubles their original length and makes it about that of the finished article. When forged the bars are brought to white heat, and are passed through semi-circular dies. The top die acts as a hammer and moves rapidly up and down as the bar passes through. In rolling the bar is passed through a series of pairs of rollers, the space between each pair of rollers being so graduated that the bar is gradually reduced to the desired size. The bars have now to be bored and rifled to produce rifle barrels. Careful gauging and examination are necessary at all stages of these delicate operations. The rifling of our service Enfield short rifle consists of a series of five spiral grooves, cut to a depth of less tnan oneone hundred and fiftieth of an inch on the inner surface of the barrel. These grooves are cut by a special " rifling" machine, in the use of which great care has to be exercised. The depth and amount of twist given to the spiral grooves must be very accurate, and careful examination is given the finished barrel by experts to see that this is so. Adjusting the Sights. Each barrel is now assembled with the particular bolt (containing tt\p striker which operates against the percussion cap of the cartridge) with which it is to,be used on the completed rifle, and the combination has to undergo " proof." We can now see the reason for the use of high carbon steel in making the bolt, as it is this portion of the mechanism which has to stand the high pressure of some 16 tons to the square inch which is exerted at the moment of the tiring of the cartridgeIn order to be sure that the barrel and bolt, when locked in position, for firing, can safely stand the force of the explosion of the ordinary service ammunition, a special " proof" cartridge, giving abnormally high pressures, is employed. A proof mark is given the barrel and bolt when this test is satisfactorily passed. The sights of the rifle have now to be adjusted. the fore sight consists of a simple little plate fitted into a block which is brazed on the barrel towards the breech end. The back sight, arranged on a hinge and marked in distances by graduations each representing 25yds," can be so adjusted as to give the necessary elevation required for the rifle to shoot at a given range. It is also possible to adjust the sight laterally to correct for the effect of wind on the bullet. W hen the sights are fixed in position the barrel is then placed in a sight-test-ing machine. This is to ascertain whether the graduations on the back eight give the correct elevations to the barrel when used for firing at various* ranges. The wooden stock of the rifle is usually j made of walnut. The wood is supplied by contractors, roughly cut to the form which it will assume in the finished product. After being examined and passed I as suitable, these embryo rifle stocks should be kept for a period of about three years I to season before being used. With all the —and there are over one hundred of them—of the rifle are finally assembled, the completed weapon has to undergo very severe tests' before being passed for service. Firing tests are carried out. in a mechanical rest, which serves to hold the rifle firmly in any desired position. At a range of 100 ft five rounds of service ammunition are fired from every rifle. Four of these rounds must strike on a vertical target within a rectangle measuring lin wide and liin high. Should the rifle not be capable" of doing this, it is rejected. Out of every ' completed batch of rifles 10 per cent, are also fired at 600 yds range. Nine rounds out of ten nnist strike within a circle cf 2ft diameter at that range. Other tests which the rifle is subjected to are designed to make sure that the rifle will be capable of undergoing the rough usage which is inseparable from active service. The rust test is carried out as follows: By cleaning with, soda water all grease or oily matter is removed from the rifle. The barrel is then filled with a saturated solution of sal ammoniac and allowed to stand in a humid atmosphere for about fifty hours. The amount of rust which has accrued by that time must not 'be sufficient to have any serious effect upon the efficient working of the rifle. The. dust test is perhaps even more drastic. With the breech block closed, and the magazine empty, th'; rifle is exposed to a blast of fine sand for the space of two minutes. After removal of any sand which has found a lodgement, by means of tapping on the ground, blowing with the mouth, or wiping with the hand.;, the mechanism must operate properly or be rejected. This test is repeated with the magazine filled with cartridges.