Projectiles are also classified by their tactical purpose. The following are descriptions of the common projectile types (fig. 2-3).

ANTIAIRCRAFT (AA).- AA projectiles are designed for use against aircraft they have no base fuze. Otherwise, they are substantially the same as the high-capacity (HC) projectiles described later.

ANTIAIRCRAFT COMMON (AAC).- AAC projectiles are dual-purpose projectiles combining most of the qualities of the AA type with the strength necessary to penetrate mild steel plate (fig. 2-3, view A). However, AAC projectiles do not have the penetrative ability of common (COM) projectiles. The type of fuzing will depend on the use. Fuze threads are provided in the nose and in the base. AAC projectiles are normally equipped with a mechanical time fuze (MTF) and an auxiliary detonating fuze (ADF). Dual-purpose action is accomplished by a time setting for airburst or by setting MTFs on "safe" or for a time longer than flight to target to permit the base detonating fuze (BDF)(delay) to function for penetration. When you substitute a point detonating fuze (PDF) for the MTF, these projectiles are converted to HC for surface burst.

ARMOR-PIERCING (AP).- AP projectiles are designed to penetrate their caliber of class A arrnor plate. A 5-inch projectile will penetrate 5 inches of armor, and so on. They are characterized in most cases by a low expIosive-charge-to-total-weight ratio and by their windshields and AP caps. Windshields are light nosepieces of false ogives designed to give suitable flight characteristics-they are made of mild steel, steel stamping, or aluminum. Windshields are screwed to the AP cap and are staked in place. AP caps are made of the same kind of steel as the projectile bodies. The cap breaks down the initial strength of the armor plate and provides support to the pointed nose of the projectile as it begins to penetrate the target. The cap also increases the effective angle of obliquity at which the projectile may hit and penetrate. The cap is peened and soldered to the nose. AP projectiles are fuzed only in the base. The fuzes must not be removed except at ammunition depots. Powdered dye colors are loaded in the windshield of most AP projectiles. These dye colors allow a firing ship to identify its splashes, since each ship is assigned a specific color. The dye is placed inside the windshield in a paper container. There are ports in the forward portion of the windshield that admit water when the projectile strikes the surface and breaks the port seals. Other ports in the after portion of the windshield are pushed out by pressure of the water inside the windshield. The dye is dispersed through these after ports.

COMMON (COM).- COM projectiles are designed to penetrate approximately one third of their caliber of armor. A 5-inch projectile would penetrate 1.66 inches of armor, and so on. They differ from AP projectiles in that they have no hardened cap and have a larger explosive cavity.

CHEMICAL.- Chemical projectiles may be loaded with a toxic, harassing, or smoke-producing agent. Of the smoke agents, white phosphorous (WP) is the most frequently used. WP projectiles (fig. 2-3, view B) are designed to produce heavy smoke and, secondarily, an incendiary effect. The small WP containers are expelled and then scattered by a delayed action burster charge that is ignited by a black powder expelling charge. Other chemical loads are dispersed in a similar manner.

PUFF.- Puff projectiles (fig. 2-3, view C) are nonexplosive projectiles used as practice (spotting) rounds. They are designed to produce dense smoke clouds approximating those of high-explosive rounds.

DRILL.- Drill projectiles are used by gun crews for loading drills and for testing ammunition hoists and other ammunition-handling equipment. They are made of economical but suitable metals and are designed to simulate the loaded service projectile represented as to size, form, and weight. They may be solid or hollow. If hollow, they may be filled with an inert material to bring them to the desired weight. This latter type is closed with abase or nose plug or both, as appropriate.

DUMMY.- Dummy projectiles are reproductions of projectiles that may be produced from a variety of materials for a number of purposes. Drill projectiles are dummy projectiles in that they are not to be fired from a gun. However, all dummy projectiles are not drill projectiles. Dummy projectiles may be made for display, instruction, or special tests.

HIGH CAPACITY (HC).- HC projectiles are designed for use against unarmored surface targets, shore installations, or personnel. They have a medium wall thickness and large explosive cavities. Large HC projectiles (fig. 2-3, view D) are provided with an auxiliary booster to supplement the booster charge in the nose of the main charge. With threads in both the nose and base, HC projectiles may receive a variety of fuzes or plugs to accomplish different tactical purposes. An adapter ring (or rings) is provided on the nose end of

Figure 2-3.-Common projectile types.

most HC projectiles to allow installation of PDFs or nose plug and ADFs with different size threads. An adapter is removed for larger fuzes. HC projectiles are normally shipped with a PDF installed in the nose. The base fuze that is shipped installed in the projectile may not be removed except at an ammunition depot.

HIGH EXPLOSIVE (HE).- Small caliber projectiles with an HE designation are designed to receive a large explosive charge. structurally, they resemble the HC type in larger caliber projectiles. They have no base fuze; a nose fuze is issued installed in the projectile.

HIGH EXPLOSIVE-POINT DETONATING (HE-PD).- These projectiles feature PDFs that may require the use of an ADF and fuze cavity liner (FCL). If the PDF is of the new, short-intrusion type, no ADF is required since its function has been incorporated. Also, the FCL has been integrated with a fuze thread adapter in some cases.

HIGH EXPLOSIVE-VARIABLE TIME (HE-VT) .- These projectiles may be fuzed with either the short-intrusion variable time fuze (VTF) and adapter or with the deep-intrusion fuze and FCL.

HIGH EXPLOSIVE-MECHANICAL TIME/ POINT DETONATING (HE-MT/PD).- This projectile is similar to the HE-MT projectile except that the nose time fuze has a point detonating backup. This backlamp causes a self-destructive action on surface impact in case of airburst function failure due to clock failure or surface impact before expiration of the set time.

ILLUMINATING (ILLUM).- ILLUM projectiles (fig. 2-3, view E) are made with thin walls. Each contains a time fuze, an ADF, a small black powder expelling charge behind the ADF, an assembly consisting of a pyrotechnic star or candle with a parachute, and a Iightly held base plug. The time fuze serves to ignite the expelling charge. Explosion of the expelling charge forces out the base and the illuminating assembly and ignites the star or candle.

ROCKET-ASSISTED PROJECTILE (RAP).- To increase the range and effectiveness of 5-inch gun systems, the RAP was developed as an addition to existing gun ammunition. It has a solid-propellant rocket motor that can impart additional velocity and provide extended range compared to standard projectiles.

SELF-DESTRUCT, NONSELF-DESTRUCT (SD, NSD).- Certain older projectiles used in AA firing have a feature that detonates the explosive filler at a designated range to prevent the round from hitting other ships in the task force. Some VTFs contain this

self-destruct device. Also, some tracers in small caliber projectiles are made to burn through to the explosive filler. In either case, the projectile carries the designation SD. Projectiles without one of these features are designated NSD.

TARGET (TAR).- These are blind-loaded (BL) projectiles. They are special projectiles designed for target practice, ranging, and proving ground tests. As target practice ammunition, they are used to train gunnery personnel. They may be fitted with a tracer (BL-T) or plugged (BL-P).

VARIABLE TIME-NONFRAGMENTING (VT-NONFRAG).- Some VT-NONFRAG projectiles (fig. 2-3, view F) are loaded to avoid rupturing the body and spreading fragments when the fuze functions. However, sometimes the projectile ogive breaks up into low-velocity fragments. They are designed for use in AA target practice, particularly against expensive drone targets, for observing the results of firing without frequent loss of the drones. These projectiles have fillers of epsom salts or other inert material to give the projectile the desired weight. A color-burst unit, consisting of pellets of black powder and a pyrotechnic mixture, is placed in a cavity drilled into the center of the inert filler. The color-burst unit is ignited through the action of the nose fuze and the black-powder pellets. The color-burst unit may be one of several colors that exits through the fuze cavity and ruptured projectile.

ANTIPERSONNEL.- The antipersonnel projectile (fig. 2-3, view G) consists of a projectile body, an expulsion charge, a pusher plate, a payload of 400 individually fuzed grenades, and a base plug. The M43A1 grenade is an airburst rebounding-type munition. The antipersonnel projectile is unique to the 16W50 gun.