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Figure 4-7. Illuminating projectiles.

1 DROGUÉ PARACHUTE SlJPPCHiT iQBOGUÉ PARACHL/TE

Figure 4-7. Illuminating projectiles.

used in automatic guns have cartridge cases with an extracting groove instead of a flange or rim.

b. In nonadjustable (fixed) rounds, the cartridge case is crimped to the projectile. In adjustable (semifixed) rounds, the case is fitted free to the projectile. In separated ammunition, the case is plugged and separate from the projectile. Having a nonadjustable propellant charge, separated ammunition may be considered a special type of fixed ammunition.

c. Brass or steel cartridge cases of special composition are processed to provide obturation in recoil-type weapons. Obturation, expansion of the cartridge case against the chamber wall under pressure of burning propellant gases, prevents escape of these gases from the rear of the weapon.

d. The cartridge case in recoilless weapons either is perforated or has a rupture disk to allow propellant gases to escape through nozzles in the breech of the weapon. The interior of the perforated type of case contains a liner that covers the perforations in the case. This prevents entrance of moisture and leakage of propelling charge grains. Liners are made of various materials, such as paper, rayon, plastic, etc. In the rupture-disk type of cartridge case, the propellant is contained in a silk bag positioned around the tail boom or primer tube.

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