a. Ogive and Windshield. The forward portion of the projectile from the bourrelet to the point is called the ogive. The length of the ogive influences the flight of the projectile. In older projectiles, the generated radius of the ogive varied from 6 to 11 calibers. Projectiles of recent design, however, have long ogives of radii that exceed these values appreciably. Since kinetic-energy, armor-piercing projectiles have an ogive with a short radius, for purposes of penetration, a windshield is placed over the armor-piercing head to impart desirable ballistic qualities to the projectile.

b. Bourrelet. The bourrelet is the machined surface that bears on the rifling lands of the weapon tube. It centers the front end of the projectile in its travel through the bore. Generally, the bourrelet is located in the forward end of the projectile, immediately behind the ogive. Some projectiles of large caliber have front and rear bourrelets.

surface in contact with the lands of the bore. Only the bourrelet and rotating band bear on the lands.

d. Rotating Band. The rotating band is a cylindrical ring of comparatively soft metal, or similar substance. It may also be of steel pressed into a knurled or roughened grooves near the base of the projectile (or attached to the base of the projectile, as in the 4.2-inch mortar). The rotating band affords a closure for the projectile in the forcing cone of the weapon in separate-loading projectiles and centers the rear end of the projectile in the bore of the weapon. In fixed ammunition, the rotating band may not seat in the forcing cone until the instant of initial movement upon firing. As the projectile moves forward, the rotating band is engraved by the lands of the bore. Metal displaced during the engraving process flows into annular relief grooves (cannelures) cut in the rotating band. In the case of 4.2-inch mortar projectiles, the rotating band is bell shaped; it is expanded into the grooves of the mortar rifling by pressure of the propellant gases on a pressure plate. Since the rifling of the weapon is helical, engagement with the band imparts rotation to the moving projectile. The rotating band also provides obturation. It prevents escape of the propellant gases forward of the projectile by completely filling the grooves of the rifling. In the case of recoilless rifle projectiles, the c. Body. While generally applicable to the entire projectile, the term, body, is used to designate the cylindrical portion of the projectile between the bourrelet and the rotating band. It is generally machined to a smaller diameter than the bourrelet to reduce the rotating band is pre-engraved. Some projectiles may be provided with two rotating bands or an obturating band and a rotating band.

e. Type of Base. When the surface to the rear of the rotating band is tapered or conical, it is known as boat-tailed; when cylindrical, the projectile is described as having a square base. Nonrotating projectiles have fins at the rear for stabilization.

f. Base Plug. All base-ejection, chemical projectiles are closed at the base with steel plugs either threaded to the projectile or secured by shear pins. Some armor-piercing projectiles are also closed with base plugs. The base plug may or may not contain a tracer or fuze.

g. Base Cover. The base cover, a thin metal disk, is crimped, caulked or welded to the base of the projectile. HE rounds are provided with base covers. These give additional assurance hot gases of the propelling charge will not penetrate the base of the projectile and come in contact with the explosive filler. Caulking or sealing rings, rather than base covers, are ordinarily provided for projectiles with HE fillers and BD fuzes.

h. Tracer. A tracer in the base of some projectiles provides for observation of fire. The tracer in certain aircraft and antiaircraft projectiles contains a shell-destroying (SD) element. The tracer, after burning a prescribed number of seconds, ignites a pellet. This detonates the explosive filler

grommet liner tnt bursting charge

Figure 4-2. High-explosive projectile.

supplementary charge grommet liner supplementary charge

tnt bursting charge

Figure 4-2. High-explosive projectile.

tYEBOLT lifting plug ord d1740

tYEBOLT lifting plug ord d1740

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  • nora
    What is attached near the base of the projectile?
    3 years ago
  • cora
    What is the rotating band cannelures on a projectile?
    11 months ago

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