|NAVAL ORDNANCE AND GUNNERY, VOLUME 1
| A. General
Ammunition is the complete assemblage of the component parts, or ammunition details, which, together, make up a charge or round for any type of weapon.
Ammunition details include primers, boosters, detonators, powder, powder bags, cases, fuzes, projectiles, etc.
3A2. Classification of ammunition
Ammunition is classified by type stowage. The classification consists of the following types:
1. Gun ammunition.
2. Bomb-type ammunition.
3. Rocket-type ammunition.
4. Guided missiles.
6. Chemical ammunition.
7. Demolition material.
3A3. Gun ammunition
Gun ammunition comprises 4 types: bag, semifixed, fixed, and small arms.
The distinction between the first 3 depends on the manner in which the charges are assembled.
In bag ammunition, the primer, propelling charge, and projectile are separate units.
In semifixed ammunition, the primer and propelling charge are contained in one unit, while the projectile is separate.
In fixed ammunition, all 3 components are assembled in 1 unit.
3A4. Bomb-type ammunition
Bomb-type ammunition is characterized by thin-walled containers, loaded with relatively large bursting charges. This ammunition depends for its effect upon the destructive blast of the explosive, rather than any penetrating qualities of the container. Included in the group are torpedo war heads, mines, depth charges, and some aircraft bombs.
Some bombs are discussed in this chapter; for further information on
bombs, see Naval Airborne Ordnance, NavPers 10826.
3A5. Rocket ammunition
A rocket consists essentially of a head and a motor. The head may be solid or may contain a bursting charge. The motor contains fuel, either in the form of a large grain of powder or a liquid. The burning of the fuel releases the energy necessary for propulsion. To stabilize its flight, the rocket either has fins on its after end, or is made to spin by exhausting the motor gases through canted nozzles.
3A6. Guided missiles
A guided missile is an unmanned vehicle moving above the earth’s surface, whose trajectory or flight path is capable of being altered by mechanisms within the vehicle. Guided missiles include, besides such control mechanisms, explosive war heads and power plants, usually of the rocket or jet type.
3A7. Pyrotechnic ammunition
Pyrotechnic ammunition may be classified according to use into three types:
Pyrotechnic materials are mixtures of oxidizing agents and combustibles (powders such as magnesium and chlorate mixtures) to which other compounds may be added for such particular purposes as to color the flame or smoke.
3A8. Chemical ammunition
Included under this classification are all projectiles, bombs, grenades, candles, or other containers of compounds the purpose of which is to produce, when liberated, gas, smoke, or fire. Also, free fluids or gases released from aircraft tanks, projectors, or sprayers are designated as chemical agents.
Chemical ammunition may be designated according to the type of container, as projectile, bomb, or grenade. However, the more usual classification, and the one used for storage purposes, is according to the nature of the filling:
Group A. Persistent vesicants. Vesicants blister the skin. The usual ones are mustard gas and lewisite.
Group A-1. Nonpersistent lethal gases. These gases, such as phosgene, injure the body when applied externally, breathed, or taken internally. Protection is not required in the open for more than 10 minutes if the wind velocity exceeds 2 mph.
Group B. Lacrimators and smokes. A lacrimator such as CH (chloracetophenone) is used primarily to cause weeping and irritation of the throat and lungs. The smokes, such as FM (titanium tetrachloride) and FS (sulphur trioxide in chlorosulfonic acid) are used for screening but have an irritant and, in enclosed spaces, a toxic effect.
Group C. Spontaneously inflammable agents such as WP (white phosphorus).
Group D. Readily inflammable mixtures such as TH (thermite), which burn rapidly and with extreme heat.
Chemical warfare is a specialized field which calls for specially trained men, The storage of chemicals requires extraordinary safety precautions. Although poisonous gases were not used in World War II, the Navy was prepared for defense and for reprisal in case the enemy initiated such tactics. Chemical warfare creates many problems in ship protection and decontamination which are the responsibility of the Damage Control Officer.
3A9. Demolition material
Explosives intended for such uses as blasting, eliminating hazards to navigation and obstacles to amphibious landing, and destroying gear to prevent capture by the enemy, comprise demolition material.
The use of blasting charges is a specialized art, requiring intensive training. Demolition techniques are taught in special Navy schools and will not be discussed in detail in this text. For major blasting operations, various forms of dynamite are used; but dynamite normally is not carried aboard ship.
Half-pound demolition charge blocks, consisting of either pressed TNT or cast TNT and tetryl, are issued to ships for general use. Large demolition charges, also consisting of TNT, and assembled with half-pound booster charges, are also issued for major projects, such as scuttling vessels. Charges of both of these types are detonated by means of blasting caps, set off by electric current.
Aboard ship, in wartime, there are mechanical devices the nature of which, preferably even the very existence of which, must under no circumstances become known to the enemy. Because highly classified instruments must be completely destroyed if capture or abandon ship is imminent, tiny bombs, called destructors, are attached to them, to be actuated at a moment’s notice. Usually, they contain lead azide or TNT-tetryl, with proper electric ignition elements.
3A10. Shaped charges
Relatively small quantities of explosive known as shaped charges can be made to pierce heavy steel plate by employing them as shaped charges which direct the explosive force into a small and concentrated jet. This jet supplies a directional damaging action.
|In an ordinary bursting charge the expanding detonation wave proceeds outward from the point of detonation, producing stresses on all portions of the enclosing case. The casing bursts into fragments under the action of these enormous forces. In a shaped charge, however, a portion of the case (fig. 3A1) farthest from the detonator is in the form of a regular cavity (usually a cone, hemisphere, or V-shaped groove) so that the detonation wave fronts impinging progressively over that portion of the case will cause compression toward the center of the cavity. Under the influence of this high-velocity compression, the portion of the case forming the cavity and known as the liner gasifies under the extreme pressures and temperatures. Most of it squirts forward in a narrow jet away from the advancing detonation wave. The front of this jet is composed of a large number of gaseous metallic particles moving at speeds of 20,000 to 30,000 feet per second. This is followed by the slug, consisting of moving particles, the residue of the highly compressed liner (or slug), and fragments from the skirt of the liner. Penetration is achieved when the high-velocity jet particles impinge upon the target somewhat in the manner that a stream of machine gun bullets entering the same hole would penetrate an earth bunker. The slug plays no role in penetration. Although confinement increases the penetration of the jet in some cases, the increase is slight and most shaped charges have only light confinement. A well-designed shaped charge will penetrate armor up to three times the diameter of the cone.
One important factor in the effectiveness of a shaped charge is the distance of the charge from the target surface at the instant of detonation. This distance, called stand-off distance, is necessary to permit effective focusing of the gaseous jet.
In demolition charges the stand-off is obtained by legs which hold the shaped charge at the proper distance. When a shaped charge is employed in gun projectiles or rockets, the nose will begin to crush before the fuze can detonate the charge. The nose is therefore longer than the required stand-off distance by an amount calculated to allow for this crushing between time of impact and fuze functioning. In general the stand-off distance at the time of detonation should equal the diameter of the shaped-charge cone.
In addition to the penetrative properties of the shaped charge, the accompanying blast and fragmentation are important considerations. One new 5-inch rocket head is multipurpose in that it can be used for blast damage, fragmentation damage, or defeat of armor by shaped charge effect.
3A11. Miscellaneous types
Under this heading are grouped a variety of types for special purposes such as impulse ammunition, blank ammunition, trench warfare ammunition, and dummy ammunition.
An impulse charge is a propelling charge designed to project a missile a short distance. It usually consists of black powder and is assembled in a cartridge case with primer. Torpedoes are propelled from above-water torpedo tubes by impulse charges. Impulse charges are also used for propelling depth charges.
Trench-warfare ammunition, still so designated in spite of the change in the concept of trench warfare, includes hand and rifle grenades and mortar ammunition. It is issued to Marines and special landing forces.
Blank ammunition contains no projectile but consists of a cartridge case with primer and powder charge. It is used to make a noise for saluting, or a smoke for signaling, and for training exercises.
Dummy ammunition includes any type of ammunition or any ammunition detail assembled without explosives. This type is used for training and test and is carefully marked so that it will not be confused with service ammunition.
B. Propelling Charge
3B1. Gun ammunition
Propelling charges with their containers, primers, projectiles, and projectile fuzes are the major components of a complete round of gun ammunition, whether bag, semifixed, or fixed.
Each of these components will be examined in some detail in the remaining sections of this chapter.
Each of the many naval guns is provided with its own associated ammunition, designed in normal service use to impart to its projectile a specified velocity at the muzzle called initial velocity (abbreviated I. V.). Special powder charges may also be provided for use in experimental work, shore bombardment, or target practice when reduced velocity is desired. Unless such reduced charges are specifically designated, it will be assumed throughout this discussion that service I. V. are meant.
Figure 3B1 shows typical rounds.
|3B2. Bag ammunition
In bag ammunition the propelling charge is a separate unit. Large guns require large quantities of propellent powder to attain required projectile initial velocity. If the total amount of powder required for a 16-inch gun were placed in a single rigid container, the size and weight would make loading exceedingly difficult and slow. By packing the powder grains in fabric bags, it is possible to divide the charge into units each of which can be expeditiously handled by one man.
Bag charges are used in the United States Navy at the present time in some 8-inch guns and all guns larger than 8-inch.
As recently as the beginning of World War II, bag-type 5- and 6-inch guns were still in use.
The largest guns in present use, the 16”/50 caliber on the newest battleships, use six powder bags with each projectile.
3B3. Powder bags
The material used for powder bags is silk, because only this fabric will completely burn away when combustion of the charge takes place, leaving no smoldering residue to cause the premature explosion of the next charge loaded. Each bag is roughly cylindrical in shape. One end consists of an ignition pad containing black powder quilted into the fabric so as to keep the black powder evenly spread throughout the pad. Light-weight cloth, dyed red, is used for the ignition pad. A heavier weight of fabric is used for the rest of the bag. Bags are fitted with handling straps and lacings, which can be used to take up any slack in the bag.
Powder may be placed in the bags in either of two ways. It may be dumped in with no regard for the positioning of the individual grains; this produces an unstacked charge. Or the grains may be arranged in layers with the axis of each grain parallel to the axis of the bag; this is a stacked charge. The latter results in a smoother, more compact bag and provides for faster, more complete, and more symmetrical ignition.
The firing of the separate primer used with bag guns can be relied on to set off the black powder in the ignition pad, but may not be sufficiently potent to initiate combustion of the smokeless powder grains directly. It is essential, therefore, that each bag of a charge be loaded into the gun with the ignition pad aft, facing the breech plug and within a few inches of the next bag or of the breech plug and primer. This factor also dictates that the total length of the powder bags comprising a charge should be nearly equal to the length of the chamber of the gun. When, therefore, a reduced charge is made up, the number and length of the powder bags are unchanged, but the diameter of each bag is reduced.
The powder bags used in a 16”/50 caliber gun are shown in figure 3B2. The markings on such a bag should be noted. Those on the body of the bag indicate the designation of the gun, the index or identification number and the weight of the smokeless powder, the fraction of a full charge represented by the bag and whether that charge is service or reduced, the initial velocity for which the charge is designed, and the initials of the inspector. Markings on the ignition pad indicate the number of grams of black powder contained therein.
|3B4. Powder tanks
Storage of smokeless powder must be both airtight and watertight if standard performance is to be maintained. The diphenylamine stabilizer contained in smokeless powder prolongs the life of the powder but does not prevent deterioration under adverse conditions. Since powder bags are neither airtight nor watertight, they are stored in tanks. These powder tanks are, therefore, important pieces of ordnance equipment which must be properly maintained. Leaky tanks admit moisture and air and allow ether and alcohol volatiles to escape.
Several types of tanks are used, but all fulfill the same basic powder-storage requirements. Top covers are variously constructed but all are designed to permit quick opening, because the number of loaded tanks allowed to be open at any one time is strictly limited by safety precautions. All powder tanks have handling aids, the large tanks having lugs to fit slings and the smaller ones having handles.
Tanks for powder bags contain wooden spacers to prevent building of a static charge which might ignite the powder by a spark.
(Bag movement within the tank during handling causes the static charge. The spacer separates the igniter pads from the end of the tank to prevent sparking which would ignite the black powder in the pads.)