The last type of projected munition is separate-loading. In separate-loading ammunition, the major components
(the projectile, the propelling charge, the primer, and the fuze) are issued individually. After the fuze is assembled
to the round and the propelling charge is adjusted for the proper range, the components are loaded into the
weapon system one by one.
Physical Characteristics of Projected Munitions
An understanding of the physical characteristics of a round of ammunition is important because of the relationship
between these characteristics and the round's designed purpose. As shown in Figure 2-11, these characteristics
include the ogive (or windshield), the bourrelet, the body, the rotating band, the obturating band, the base, the
base plug, and the base cover.
Ogive (or Windshield). The ogive (or windshield) is used to provide desirable ballistic qualities to a round.
The ogive is the forward part of a round, from the tip of the round to the bourrelet. Due to the blunt nose on
armor-piercing, kinetic-energy rounds, a windshield is used as a false ogive.
Bourrelet. The bourrelet is that portion of a round that bears on the rifling lands and grooves of a weapon. It
centers the front end of a projectile as it travels through the bore. The bourrelet is usually located on the forward
section of the projectile, immediately behind the ogive. Larger-caliber projectiles may have two bourrelets, one in
front and one in the rear.
Body. The word "body" is generally applied to the entire length of the projectile. However, the term is
specifically used to designate that portion of the projectile between the bourrelet and the rotating band. It is
normally machined to a smaller diameter than the bourrelet to reduce the surface of the projectile that comes in
contact with the bore. The body of the round contains its filler.
Rotating Band. The rotating band is a cylindrical ring of comparatively soft metal or a similar substance.
However, it may also be of steel and pressed into grooves near the base of the projectile. As the projectile moves
forward, the rotating band engages the lands of the weapon and imparts spin to the projectile.
The rotating band also provides obturation for the projectile, which means that it prevents the escape of the
propellant gases forward of the projectile by completely filling the grooves of the rifling. In the case of recoilless
rifle rounds, the rotating band is pre-engraved. Some projectiles may be provided with two rotating bands, or a
rotating band and an obturating band. Mortars may have either a rotating band or, more commonly, an obturating
band.
Obturating Band. All spin-stabilized mortar rounds use obturating bands as gas check bands. The
obturating band swells to provide a positive gas stop between the mortar tube walls and the body of the round.
Base. There are three types of bases used on projectiles. When the round remains the same cylindrical
diameter all the way to the end of the base, it is described as having a square base. If the base is tapered or
conical, it is described as a boattail base. Non-rotating projectiles have a tail boom and fins instead of a base.
Base Plug. Base plugs are used with base-ejection projectiles. Base plugs are steel, and they may be either
threaded into the projectile or secured through the use of shear pins. Rounds with base plugs may contain
leaflets, chemical compounds (either illumination or smoke), or submunitions. Some armor-piercing rounds also
have base plugs. Base plugs may contain a tracer element.
2-15
MM0145
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