Military


Gun Ammunition

Projectiles

The projectile is the component of ammunition that, when fired from a gun, carries out the tactical purpose of the weapon. While some types of projectiles are one piece, the majority of naval gun projectiles are assemblies of several components. AU the projectiles discussed (by classification) in this chapter have several common features, as described in the following paragraphs and in the figure below.

Figure 1

OGIVE - The ogive is the curved forward portion of a projectile. The curve is determined by a complex formula designed to give maximum range and accuracy. The shape of the ogive is generally expressed by stating its radius in terms of calibers. It maybe a combination of several arcs of different radii.

BOURRELET - The bourrelet is a smooth, machined area that acts as a bearing to stabilize the projectile during its travel through the gun bore. Some projectiles have only one bourrelet (forward); the rotating band serves as the bearing surface in the rear. Still other projectiles have one bourrelet forward and one or two aft, the after one being located adjacent to and either forward and/or aft of the rotating band. Bourrelets are painted to prevent rusting.

BODY - The body is the main part of the projectile and contains the greatest mass of metal. It is made slightly smaller in diameter than the bourrelet and is given only a machine finish.

ROTATING BAND - The rotating band is circular and made of commercially pure copper, copper alloy, or plastic seated in a scored cut in the after portion of the projectile body. In all minor and medium caliber projectiles, rotating bands are made of commercially pure copper or gilding metal that is 90 percent copper and 10 percent zinc. Major caliber projectile bands are of cupro-nickel alloy containing 2.5 percent nickel or nylon with a Micarta insert. As a projectile with a metallic band passes through the bore of the gun, a certain amount of copper will be wiped back on the rotating band and will form a skirt of copper on the after end of the band as the projectile leaves the muzzle of the gun. This process is known as fringing and is prevented by cutting grooves, called cannelures, in the band or by undercutting the lip on the after end of the band. These cuts provide space for the copper to accumulate. The primary functions of a rotating band are:
1. To seal the forward end of the gun chamber against the escape of the propellant gas around the projectile,
2. To engage the rifling in the gun bore and impart rotation to the projectile, and
3. To act as a rear bourrelet on those projectiles that do not have a rear bourrelet.

BASE - The base is the after end of the projectile. A removable base plug is provided in projectiles that are loaded through this end. A fuze hole maybe drilled and tapped in the center of this base plug. Projectiles with large openings in the nose for loading through that end require no base plug. In such cases, however, the solid base of the projectile may be drilled in the center to receive abase fuze or tracer if desired The edge formed by the sidewalls and the base is usually broken slightly to give additional range. Some projectiles are tapered aft of the rotating band, a shape known as boat tailed. Projectiles with plastic bands may have full caliber boat tails for optimum aerodynamic shape.

Types of Projectiles

Projectiles are also classified by their tactical purpose. The following are descriptions of the common projectile types.
Figure 2

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, 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 explosive-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, 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, 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, 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 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, 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, 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, view G) consists of a projectile body, an expul- sion 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 gun.

Propelling Charges

Propelling charges are mixtures of explosives designed to propel projectiles from the gun to the target. In fixed ammunition, the propelling charge and projectile are assembled together in a case and handled as one unit. The principal component parts are the brass or steel cartridge case, the primer, and the propellant powder charge. In the separated ammunition, the propelling charge and projectile are assembled separately-they are stowed and handled as separate units until they are loaded into the gun. The propelling charge of the separated ammunition round consists of the propellant primer, details, and closure plug assembled into the metal case. The propelling charges of separate loading ammunition are made up in sections separate from the projectile and primer. Propelling charges for all calibers of ammunition have some common features. The basic type of charge is case ammunition. Saluting, reduced, and clearing charges have components that are the same as case ammunition, so they are included with case ammunition.

Propelling charges for small and medium caliber guns are assembled with primer and powder enclosed in a brass or steel container called a cartridge case. Assembly of the entire charge in a single, rigid, protective case increases the ease and rapidity of loading and reduces the danger of flarebacks. Also, the case prevents the escape of gases toward the breech of the gun; it expands from the heat and pressure of the burning powder and forms a tight seal against the chamber.

In case-type propelling charges, the propelling charge and primer are contained in a cylindrical metal cartridge case. This ammunition is of two types-fixed and separated. In fixed ammunition the primer, propelling charge, and projectile are assembled into a single unit that may be loaded into the gun in a single operation, In separated ammunition, the primer and propelling charge are contained in a cartridge case as a separate plugged unit; the projectile is also a complete, separate unit.

A complete round of separated ammunition consists of two pieces-a projectile and a cylindrical metal cartridge case sealed by a cork or plastic plug. Separated ammunition is used in 5-inch guns and their cases are kept in airtight tanks until they are to be fired.
Figure 3

A complete round of fixed ammunition is one piece, with the cartridge case crimped to the base of the projectile. Fixed 76-mm rounds are also kept in tanks, but smaller calibers and small arms are stowed in airtight boxes, several rounds to a box.

The insides of both the fixed and separated ammunition cartridge cases are quite similar. Figures 3 and 4 show the main components of both types of cartridge cases. The base of the primer fits into the base of the case so that the firing pin of the gun lines up with and contacts the primer when the breech is closed. A black-powder ignition charge runs the full length of the perforated stock or tube of the primer.


Figure 4

The 5-inch ammunition being issued to the fleet is assembled with case electric primers. The most notable exception to this practice is the 76-mm round that uses a percussion-only primer. Look at the cartridge case in figure 4 again. When the gun fires, the case expands under the powerful pressure of the burning propellant gas, then must contract so that it can be removed from the chamber. It must not stick to the chamber walls nor may it crack. For a long time, only seasoned brass cases could be relied on to perform correctly. During World War II, when the supply of brass became critical, metal- lurgists developed a steel case that has since almost completely replaced brass. Regardless of what cases are made of, used cases are often called "fired brass." Steel cartridge cases are no longer reloaded and reused; however, since the cartridge tanks are required for reuse, the cases maybe returned in the empty tank for the scrap value.

Immediately after firing and before returning the cases to their tanks, the ejected cases (76mm and larger) should be stood on their bases to permit residual gases (small amounts left over after firing) to escape completely. Other cases should be replaced in the original containers, tagged, and stowed.

In the center of the base of the case is the threaded hole for the primer. The case tapers slightly toward the forward end so that it can be withdrawn from the chamber without binding. A rim at the base is engaged by the extractors of the gun. In fixed ammunition, the case often has a bottleneck in which the projectile is crimped.

The propellant powder in the case is the seven-perforation kind we have already discussed. (Small caliber grains have one perforation.) The powder is weighed out with great precision and loaded into the case at the ammunition manufacturing facility. Since it does not take up all the space inside the case and since it would be dangerous for the powder to have a lot of room to rattle around in, it is tightly packed and sealed under a cardboard or pyralin wad The wadis kept tight by a triangular cardboard distance piece. The distance piece bears up against the plug that closes the mouth of the case. Infixed ammunition, the case is sealed by the projectile base.

A small amount of lead foil included in each propelling charge functions to clear the bore of the metal fouling that scrapes off the projectile rotating band onto the rifling as the projectile passes through the barrel.

Reduced Charge - A reduced charge is one that contains less than the service load of powder. Reduced charges are often used to fire on reverse-slope targets and may be used in target practice to decrease wear on the gun.

Clearing Charge - When a round fails to seatfully upon being rammed into the gun chamber (preventing closure of the breech) or when the propelling charge fails to function, the projectile maybe fired by extracting the full-sized case and loading a clearing charge that is shorter.

Saluting Charge - These are charges used when firing a gun to render honors. Since no projectile is involved in such firing, the charge consists of a cartridge case containing a black-powder load and a primer. Ships normally employ 40-mm for saluting. Saluting charges for these guns are issued completely assembled, with no replacement components.

Magazines

The term magazine applies to any compartment, space, or locker that is used, or intended to be used, for the stowage of explosives or ammunition of any kind.

The term magazine area includes the compartment, spaces, or passages on board ship containing magazine entrances that are intended to be used for the handling and passing of ammunition. The term is also used to denote areas adjacent to, or surrounding, explosive stowages, including loaded ammunition lighters, trucks, and rail- road cars, where applicable safety measures are required.

Magazines are arranged with regard to facility of supply, the best obtainable protection, and the most favorable stowage conditions.

Magazine types:

There are many different types of magazines provided on ships. Each magazine is designed specifically for the type of ammunition it is to contain. The three main types of magazines are primary magazines, ready-service magazines, and ready-service stowage.

Primary Magazines

Primary magazines are designed as ammunition stowage spaces, generally located below the main deck, and insofar as is practical, below the waterline. They are adequately equipped with insulation, ventilation, and sprinkler systems. These spaces must be provided with fittings so that they may be locked securely. Primary magazines accommodate a vessels complete allowance of ammunition for peacetime operation.

Ready-Service Magazines

Ready-service magazines are spaces physically convenient to the weapons they serve. They provide permanent stowage for part of the ammunition allowance. Normally they are equipped with insulation, ventilation, and ammunition sprinkler systems, and should be secured by locking. The combined capacities of primary and ready-service magazines are normally suf- ficient to stow the ships allowance for war and emergencies.

Ready-Service Stowage

Ready-service stowages are those ammunition stowage facilities in the immediate vicinity of the weapon served. They include weather deck lockers, bulwark (gun shield) racks, and 5-inch upper handling rooms. This stowage normally is filled only when the weapon is to be fried. There is little security for ammunition in such stowage, and it provides the least favorable protection from the elements.

All magazines are marked by appropriate label plates showing the compartment number and the types of ammunition to be stowed therein. Insofar as is practical, magazines are designed to hold a single type of ammunition.



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