Projectiles are classified according to their calibre, type of gun for which they are intended, material of which they are made, etc., as per the following scheme used in the U.S. Army for marking cases of projectiles:
| { | Cast steel | |||||
| Inch | { | Rifle | { | Cast iron | ||
| { | Mortar | { | Common steel | { | Shot | |
| { | Armor piercing | { | Shell | |||
| { | { Rendable A.P. |
| Weight empty—Lbs. |
| Capped or uncapped |
| or |
| Capped and grooved for base cover |
| or |
|
Uncapped and grooved for base cover Base } Fuze Point } |
Manufacture of Projectiles
While a high state of development has been attained in the manufacture of armor-piercing shells attention will be confined to their manufacture in so much as the methods for improvement hereinafter suggested are intended to affect the physical and not the chemical properties of the material, and are, therefore, applicable to all projectiles in which the stresses to be resisted exceed the resisting powers of the projectiles as at present manufactured.
The function to be performed by an armor-piercing shell is that of fully penetrating, without disruption to itself, an armor plate in thickness equal to, at least, the calibre of the shell in question, and then be in condition for effective bursting.
The following extracts from the Army and Navy specifications pertain to:
Material and Workmanship
(Art 20, O. D., U.S.A.)
The projectiles must be of forged steel, sound, and free from cracks, seams, and other defects [ 1].