Fixed Barrel

Figure 4-4. Elementcrry Form of Gun Having Chamber Separate From Barrel.

chamber gap -

explosion chamber cartridge

Figure 4-4. Elementcrry Form of Gun Having Chamber Separate From Barrel.

opening and the barrel bore are not in good alignment at the instant the projectile passes from the chamber into the barrel, the projectile will encounter an interference in its movement which could cause serious damage to the gun or projectile or at least cause shocks which would upset the accuracy of fire. (This type of defect is what causes the "shaving of lead" so commonly experienced in old or badly constructed revolver hand guns. )

In addition to accurate alignment between the chamber opening and barrel bore, it is also important for the explosion chamber to be positioned accurately so that the correct spacing exists between the rear face of the frame and the base of the cartridge when the cartridge is fully seated in the chamber. If the base of the cartridge projects too far out of the rear of the explosion chamber, it may interfere with the movement of the chamber into the base of the cartridge case is not rigidly supported by the frame of the weapon, the high pressure within the case continues to act against the base and creates tension on the ease walls. Since the chamber pressure may be 50,000 pounds per square inch or more and since this pressure acts on a considerable area at the base of the case, the force exerted on the base is so tremendous that any resistance to stretching offered by the tensile strength of the thin walls of the case is entirely negligible. Therefore, the case material stretches quite readily and the base continues to move to the rear while the thin forward portion of the case remains stuck to the chamber wall. If the space between the base of the cartridge case and the supporting surface of the frame was originally too great, the case will stretch beyond the ultimate limit of the strength of the material from which it is made and will be

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