Downloaded from https://www.everyspec.com \ CHAPTER 2 REGIONS OF THE GUN TUBE 4. A gun tube may be divided into four regions: tubes. The main and largest compartment, the the front portion or bore through which the pro- chamber body, houses the propellant and igniter. jectile travels when the round is fired; the rear Parts b, c, d, and e, of Figure 2 show complete portion or chamber which houses the roand before rounds positioned in various tube chambers.
Artillery firing; the rear opening or breech through which the tubes using separate loading ammunition have the ammunition is loaded; and the 'front opening or inner chamber wall cylindrical or conical, the mini- muzzle from which the projectile emerges. In re- mum diameter of either contour being limited to coilless guns the rear opening or nozzle provides the maximum diameter of the forcing cone. If for reeoillemness. Exceptions do prevail with respect conical, the inner surface may be the extension of to the functions of these regions particularly with the forcing cone. On the other hand, for tubes firing J breech opening and loading technique.
For example, fixed and sernifixed ammunition, the clearances be- most mortars are muzzle loaded and have per- tween chamber and cartridge case and the slopes of manently closed chambers. Figure I is a typical tube the chamber walls are critical, since the cartridge showing the regions applicable to conventional guh case walls, by expanding, seal in the propellant tubes. gases, but must recover sufficiently after firing to assure easy case extraction. This is particularly A. CHAMBER true in small arms where small clearances are de- 5.
After loading but prior to firing, the part of sired along the tapers including those in which a the projectile forward of the rotating band or its definite longitudinal interference is desired at the equivalent is located in the bore, and in the case of first shoulder. During loading, the force of the recoilless ammunition, the pre-engraved band also breechblock may actually collapse the case slightly rests in the bore. The remainder of the round rests in this region to obviate the likelihood of axial in the chamber, which, except for revolver type failure of the case.
This collapsing action is called guns, is integral with the bore and consists of the crush-up and contributes to easy case extraction. chamber body, the first shoulder, the centering cylinder for artillery or the neck for small arms, B. B]EECH RING ATTACHMINT the second shoulder, bullet seat, and the forcing 6. The chamber is closed by a breechblock or cone, (Fig. 2a). The forcing cone is a conical frustum bolt or, as in recoilless weapons, by the nozzle unit. whose slope extends through the origin of rifling A breech ring supports the breechblock. The breech and intersects the bore surface. Engraving of the ring is threaded to the outside of the chamber wall.
rotating band occurs here, The section immediately Its counterpart in some small arms is the receiver to the rear of the bullet seat is called the centering which houses the bolt. The nozzle unit of a recoilless cylinder or neck. It is just large enough to receive tube may be attached directly to the rear of the the rotating band or the neck of the cartridge case. chamber wall or to a modified breech ring. These This feature is not always found in heavy artillery elements are attached to the tube so that the re- B--REECH FIGUIlIR 1. Typical Gun Tube Showing Regions. 2 * -. *!,*,,**. .~*~****-**