Excerpt from Handbook of the 6-Inch Howitzer Materiel: Model of 1908 and 1908mi; With Instructions for Its Care The breechblock is of the interrupted-screw type and is provided with four-threaded and four-slotted sectors. The front end of the axial recess in the block for the hub of the block carrier is closed by a bushing. Two vent holes leading from a cavity in the bushing rearwardly through the breechblock permit the escape of gas from a ruptured primer: On a semicircular boss on the rear face of the breechblock are cut gear teeth, in which the gear teeth of the operat ing lever bevel gear mesh. The lower end of the circular boss on which the gear teeth are cut serves as a step to limit the rotation of the block to the unlocked position. This lower end of the circular boss comes in contact with a hardened steel step riveted to the inner face of the block carrier. A radial lug or tooth projects from the inner surface of the breechblock and engages an L-shaped groove cut in the hub of the block carrier, so that when the mechanism is un locked no relative movement between the breechblock and carrier can take place. In order to surely maintain this relation between the breechblock and block carrier, a block latch, pivoted on the inner face of the carrier in the upper left - hand quadrant, engages a notch or shoulder cut in the rear face of the block adjacent to the boss on which\the gear teeth are cut. This latch is so pivoted that as the mechanism is swung free from the howitzer it moves forward suffi ciently to engage the notch in the block and also to cause the forward plane of the latch to project forward of the front face of the block carrier; consequently when the mechanism is swung to the closed position the front face of the latch comes in contact with the rear face of the breech of the howitzer, thus forcing the latch out of the notch in the breechblock back into a recess in the carrier, and by continuing the motion of closing the mechanism the breechblock is free to rotate on the hub of the carrier and engage its threads with those in the howitzer. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.