Existing types

The following types of projectiles may be encountered at activities in the U.S. Naval Service:

Armor-Piercing: These projectiles are designed to penetrate an equal caliber of Class A armor plate, according to test practice. The characteristics:

Over-all color

Sizes

Explosive filling

Load factor

Fuzing

Since it is desirable to keep the center of gravity of a projectile to the rear of (or in the immediate vicinity of) the center of the form, and as a relatively long ogive is con-ducive to long range, it has been advantageous to adopt light nose pieces of flase ogi-vals termed windshields. The windshield is made of either forged mild steel, steel stamp-ing, or aluminum. It has no special strength other than to prevent destruction during handling and set-back on firing. Windshields are screwed to the cap and are "set" by a center punch.

The armor-piercing cap is secured to the projectile by peening the skirt of the cap in-to notches cut into the ogive of the body and by soldering the cap to the body with a special solder of low melting point. Such solder prevents the soldering heat from drawing the temper of the body. Caps are made, in general, of the same kind of steel as are the projectile bodies. The cap acts to break down the initial strength of the armor plate, allowing the nose to reach an already strained surface. It also provides powerful circum-ferential support to the point and nose as they begin to penetrate the hard face, main-taining the support until they are well into the plate. In addition, the characteristically blunt outline of the cap serves to increase the effective angle of obliquity at which the projectile may hit and still penetrate.

The body is of high-quality alloy steel, carefully forged and heat-treated, since it is the part which does the actual penetration. Between the forward bourrelet and the ro-tating band or rear bourrelet, the diameter of the body is slightly reduced in order to pro-vide a general clearance from the bore of the gun. The bourrelet is the bearing surface of the projectile and rides on the lands of the rifle. This bearing surface is usually about one-sixth caliber in width, and its surface is generally ground to a fine finish to reduce friction and minimize wear on the lands of the gun. With the major caliber projecitles, it has become standard practice to provide a rear bourrelet or bourrelets in addition to the forward bourrelet. Rear bourrelet or bourrelets will be just before and behind the rotating band, providing better support in the gun and during the moment of ejection at the muzzle.

The rotating band has three primary functions: to seal the bore, to position and cen-ter the rear end of the projectile, and to roatate the projectile. A secondary function is to hold the projectile in place during loading and elevating for fire. The rotating band is made of commercially pure copper, or of cupro-nickel alloy containg 25% nickel, or in some cases a gilding metal consisting of 90% copper, 10% zinc. As a general rule, rotat-ing bands are about one-third caliber in width.

The base plug closes off the explosive cavity and holds the base fuze or base fuze adapter. Both the base plug and the base fuze adapter, if used, are sealed in place with a gas seal ring similar to that used on the base fuze.

The base fuze in inserted through the base plug or base fuze adapter and is desigend to detonate the projectile after penetration. After insertion, it is closed with a gas check ring of copper and lead put in under hydraulic pressure to prevent the propelling gases from affecting the explosive filling.

Armor-piercing projectiles and common projectiles having a windshield may carry a spotting dye which colors the water on impact in order that observers may spot the fall of shot. The spotting dye in powder form is placed in the windshield before it is screwed on to the nose of the projectile. Water forces through the inlet holes covered by copper covers, dissolves the dye, and fores it out the outlet holes.

Special Common: The term "Special Common" is not an official designation of the Bureau of Ordnance, which places this and all other types of Common projectiles in a single class. The "Special Common" term, however, is widely employed by ordnance acti-vities to describe those Common projectiles which are equipped with both windshields and hoods for windshield attachment.

These projectiles are designed to penetrate approximately one-third to one-half their caliber of armor. These projectles differ from Armor-Piercing projectiles in that they do not have an armor-piercing cap and have a larger explosive cavity. Characteristics:

Over-all color

Sizes

Explosive filling

Load factor

Fuzing

Common: These projectiles are designed to penetrate approximately one-thrid their caliber of armor. They differ from Armor-Piercing and Special Common projectiles in that they have no cap or hood; the windshield threads directly to the body. Also, the explo-sive cavity is slightly larger. Characteristics:

Over-all color

Sizes

Explosive filling

Load factor

Fuzing

Old types: In addition to these Special Common and Common projectiles described above, certain types of old Common projectiles are still in use in the Naval service. These projectiles have neither cap nor windshield, are colored slate over all; are loade with Ex-plosive D or black powder/TNT mixture. In the latter case, they are fuzed with a base ig-nition fuze. This latter type is found in the 1-, 3-. and 6-pounder projectiles and in the 3-, 4-, and 5-inch sizes.

High Capacity: These projectiles are designed to have a minimum wall thickness, and the largest explosive cavity consistent with the force to set-back. They are assembled, gernally, with no-delay base fuzes, tracers, steel nose plugs, and auxiliary detonating fuzes. The steel nose plug may be removed and a point detonating or nose time fuze substituted. These projectiles are used for shore bombardment, for antiaircraft guns, and for use against light ships and surface craft. The 3-inch High-Capacity has no base fuze. Characteristics:

Over-all color

Sizes

Explosive filling

Load factor

Fuzing

Only variation from the no-delay base fuzes is the Base Detonat-ing Fuze Mk 48, with a 0.01-second delay, currently being as-sembled in 8" through 16" H.C. projectiles for bombardment. In the 12", 14", and 16" H.C. projectile, there is a TNT booster be-neath the auxiliary detonating fuze, requiring an additional adap-ter ring