PROJECTILES. (See also, ARMOR; ORDNANCE GUN, PNEUMATIC.) Material. —A little more than twelve years ago chilled cast-iron projectiles were considered all that could be desired for work upon the wrought-iron armor of that period, and, in fact, an extensive series of experiments made in England tended to prove that against this type of armor the chilled iron was fully equal to the steel shell in normal. while it was slightly superior in oblique fire. These experiments also included tests of chilled-iron projectiles against steel plates, with the result of a decision being reached that "steel shell are absolutely necessary for the attack of steel-faced armor." France and Germany were the earliest in the field with steel armor-piercing projectiles.
In the first-named country several concerns are engaged in shell making, each practicing some special mode of treatment, or using some particular chemical combination. At Terre Noire, for example, the steel is oil hardened, but not forged, and the quality varies in dif ferent projectiles, being softest in the largest calibers; but the degree of hardening varies also, so that the final product possesses nearly the same degree of hardness in all cases. St. Chamond projectiles are generally made of crucible steel, forged, and oil hardened; but here the quality of the steel is the same for all calibers, and the hardening process differs. That for the 34-cmt. shell is described as follows: The projectile is brought to a cherry-red heat throughout, plunged in oil, and kept immersed until cold; it is then brought again to a cherry-red and dipped in cold water as far as the front band, where it is kept eight or ten minutes: finally it is wholly immersed in oil until cold.
Krupp projectiles are of crucible steel, and the final process is oil hardening; it is said that a file will not bite anywhere on the surface. The use of steel has lately been extended to the manufacture of common and shrapnel shell also: the thickness of the shell walls is thereby greatly reduced, while retaining all the strength of the cast-iron projectile, so that the interior capacity for bursting charge or bullets, and consequently the efficiency of the shell, has been correspondingly increased. The projectiles are generally made of cast
steel, but in England the difficulty of procuring sound small castings led to the introduction of forged steel for the smaller calibers, and the superiority of these over the cast-steel ones was so marked that they are now made for all calibers.
In this country cast-iron shell have been produced with facility at the various government establishments for a number of years. The efforts to obtain cast-steel shell were long unsuc cessful, the first samples being all rejected on account of imperfections in castings. For the past two years, however, the specimens submitted have passed inspection, and the certainty of the necessary supply is now guaranteed. An attempt has also been made to produce chrome steel of domestic make suitable for armor-piercing projectiles, but nothing altogether satisfactory resulted until quite recently. Now it is thought that in the Carpenter projectiles, by adopting methods of manufacture that originated in this country, rather than those that are used in France, the requirements of the French standard have not only been reached bnt surpassed. The armor-piercing projectiles are all carefully turned and gauged, which renders them very much more expensive than common shell.
armor-piercing projectiles of the Holtzer and Firminy processes have been used in all of the principal armor-plate trials, and are still considered unequaled by England, France, Russia, and Spain. With these sharp-pointed projectiles the only object sought has been penetration on normal impact, and but little attention has been given to the effects of blows delivered at sharp angles. The most important tests of such effects were carried out several years ago at the naval ordnance proving ground with projectiles having heads of various shapes, but as yet the results have apparently been put to no practical use. The decided results obtained at late armor trials have caused some little discussion as to the practicability of using flatter-headed projectiles for oblique attack on armor.