=The Latch-cover= (_i_) is a separate piece which covers the latch and its spring, and is secured to the carrier-ring by two screws (_j_). On removing this plate the latch and spring can be taken out. =The Latch= (_f_ in Fig. 32) fits in a recess in the carrier-ring on the right side. It is acted on by a spring (_b_, Fig. 33), which pushes it constantly toward the axis of the carrier-ring. Its inner end or stem (_a_) rests on the surface of one of the slotted sectors, except at the end of its travel, when it drops into the corresponding recess in the block. As long as its stem rests on the surface of the sector its outer end or nose projects beyond the exterior surface of the carrier-ring, and, entering a recess in the jacket, locks the carrier-ring to the jacket. When the stem drops into its recesses, the nose of the latch is withdrawn by the action of the spring and the carrier-ring is unlocked. The front face of the latch has a recess (_h_), into which fits a hardened stud (_s_) that is screwed into the rear face of the jacket. This stud acting against the recess lifts the latch out of its locking-recess in the breech-block, and holds it in a position such that the stem can pass up the inclined groove. In order that the stud may act on the latch, a hole (_g_) is drilled through the front face of the carrier-ring for the stud to pass through. [Illustration: FIG. 33.] The functions of the _latch-spring_ have already been explained. The =Stop= (_c_, Fig. 32) enters the carrier-ring on the left side between the lugs (_e_), and projects beyond the bore of the carrier-ring, entering a groove in the breech-block which is cut for it. This stop limits the travel of the block to the rear in withdrawing it, and also limits its rotation. The =Hinge-pin= enters the lugs (_e_) of the carrier-ring and a corresponding lug on the jacket from below, and the carrier-ring swings around it in opening. The bore is the diameter of the ring across guide-sectors. The exterior taper forms the surface of contact of carrier-ring with jacket. The lugs (_e_) are the bearings for the hinge-pin. The carrier-ring, as its name indicates, carries the breech-block when the latter is withdrawn, and by means of it the block may be swung round out of the way for loading. [Illustration: THE DE BANGE OBTURATOR. FIG. 34.] The principal parts are: the spindle (_a_); the front cup (_f_); the rear cup (_f′_); the pad (_g_); the spring (_j_); the nut (_h_); the spline-screw (_k_). The spindle has a mushroom-shaped head (_b_), and a stem, which extends through the breech-block and terminates in a screw-thread. The breech-block is recessed correspondingly. In guns with axial vents, the vent (_c_), 0.2 inch in diameter, passes through the axis of the spindle, and the copper bushing (_d_) is inserted by pressure at the front end.