SMALL ARMS AMMUNITION Ammunition for Small Arms.—In America military small arms ammunition for rifles consists of a cartridge composed of a bottle-necked, rimless cartridge case containing a non-corrosive primer, a charge of nitrocellulose smokeless powder, and a coni cal, sharp pointed bullet having a core of lead and a jacket com posed of copper and zinc. For revolvers and pistols the bullet is not always jacketed, but may be composed of an alloy of lead, tin and antimony. For rifles, five cartridges are usually secured to gether at the head of the cases by means of a clip, thus permitting all five cartridges to be inserted in the magazine of the rifle in one motion. Small arms cartridges are usually packed in cardboard cartons of 20 to 5o rounds, or in cloth bandoliers of 6o rounds for convenient issue, and these cartons or bandoliers are in turn packed in wood boxes of i,000 to 2,000 rounds for transportation purposes.
The primer, inserted in a cup at the rear end of the cartridge case, serves to ignite the primer and contains the priming mixture. Formerly priming mixtures all contained a large percentage of potassium chlorate, but it has recently been found that this was almost the sole cause for the serious corro sion in the bores of small arms. The most recent development in primers in the United States has been the complete elimination of potassium chlorate from the priming mixture, thus making the ammunition non-corrosive.
Formerly all reliable smokeless powders were of the nitroglycerine type. While such powders have been greatly improved, the greatest advancement has been in the development and perfection of nitrocellulose powders to the point where they can now be considered the equal of any nitroglycerine powders in reliability, while having very great advantages in the matter of lessened erosion. Improved nitrocellulose powders have more than doubled the life of the barrels of small arms.
Prior to 1906 bullets for small bore military rifles were cylindrical, with a rounded nose or point. The bullets for the •3o calibre U.S. rifles of the models of 1892 to 1903 weighed 220 grains, being composed of a lead core with a jacket of cupro nickel. In 1906 the bullet was decreased in weight to 15o grains and the point was changed to a sharp form. The sharp point greatly lessened the air resistance, and the lighter weight per mitted more powder to be used, thus greatly increasing the velocity (2,25o f.s. to 2,70o f.s.), and flattening the trajectory. In 1926 a still further improvement was made in this bullet, the weight being increased to 172 grams and the form changed to a boat-tailed or streamline shape. With the same initial velocity as previously, this change in weight and form increased the maximum range of the rifle and its cartridge from 3,3ooyd. to 5,600yd., and very greatly increased the range to which the sheaf of fire from machine-guns could be effectively controlled. At the same time the material of the bullet jacket was changed from cupro-nickel to a composition of copper 90 parts, zinc 10 parts, the change doing away entirely with the metal fouling of the bores of small arms which had always been troublesome with bullets jacketed with cupro-nickel.
Improvements in sporting cartridges for rifles have paralleled the military cartridges in details. Black powder cartridges and those with heavy bullets are now obsolete. Modern cartridges are of the ultra high velocity type, employing light bullets at muzzle velocities from 2,30o to 3 , 50of t. per second. The bullets are made to expand on impact by leaving a portion of the lead core exposed at the point or by a hollow point. The continent of North America does not contain any dangerous or thick-skinned game, and hence in the United States there has been little or no development of the extremely powerful sporting cartridge, such as is needed for the heavy game of Africa and southern Asia. Instead, developments have tended towards greatly increased accuracy and very flat trajectory. Most sporting rifle cartridges now employ bullets jacketed with an alloy of copper and zinc to avoid metallic fouling, and the non-corrosive primer has become quite general in its application.
In ammunition for shotguns a progressively burning, nitrocellu lose powder has quite generally been adopted for the better grades of cartridges. This new powder has enabled the velocity to be increased several hundred feet per second, with little increase in the breech pressure, and with no bad effect on the patterns.
