Field artillery materiel

by Unknown

Operation of the Breech Mechanism. When the breech is closed and locked, the threaded portions of the breechblock mesh with the threads in the breech recess. The operating lever is held by the lower end of the operating lever handle which engages the block carrier lever catch, thus preventing any rotary motion of the breechblock at the instant of firing. The firing pin receives the blow of the percussion hammer and fires the primer. The flame passes through the vent in the obturator spindle, igniting the propelling charge. The gas pressure in the bore forces the mushroom head of the obturator spindle hard against the gas check pad causing the latter to expand and press against the walls of the chamber, forming a gas-tight joint. After the explosion the elasticity of the pad causes it to resume its former shape, allowing the obturator to be withdrawn freely from its seat when the breech is unlocked.

To Open the Breech. After the piece has been fired, and before unlocking the breech, press back the firing mechanism block safety latch, screw out the firing mechanism block and remove the used primer. The breech can not be unlocked with the firing mechanism block in place. An attempt to do so will result in jamming of the firing mechanism safety plunger. It is therefore important that the firing mechanism block should be removed before attempting to unlock the breech.

Press down on the handle of the operating lever in order to disengage it from the block carrier lever catch. Move the lever toward the rear and then to the right. In the first part of this movement, the operating lever turns freely around the hinge pin and its lug operates the rack which turns the breechblock. The threaded parts of the breechblock are thus disengaged from the threads in the breech recess. As the rack reaches the limit of its travel, the block carrier is swung on its hinge drawing the breechblock out of the breech recess. As the block carrier leaves the breech face of the howitzer the rack lock is forced by its spring into the recess in the rack preventing any further rotary motion of the breechblock in either direction. As the breech reaches its full open position the right end of the operating lever catch engages the operating lever catch, locking the breech in open position.

In loading, care should be taken to ram the projectile home and to enter the propelling charge in such a way that the igniter of the base charge will be in contact with the mushroom head of the obturator spindle when the breech is closed.

To Close the Breech. Press down on the operating lever handle to disengage the operating lever latch from the operating lever catch and move the operating lever to the left and forward. As the block carrier comes in contact with the breech face of the howitzer, the rack lock is pushed back into its seat, freeing the rack. Further movement of the operating lever forces the rack to the left, rotating the breechblock until its threaded portions mesh with the threads in the breech recess. At the end of the movement of the operating lever, the operating lever handle engages the block carrier lever catch and fastens the breech in locked position.

Insert a new primer in the primer seat plug and replace the firing mechanism block. The firing mechanism block can not be entered until the breech is closed and locked. Any attempt to do so may cause damage to the firing mechanism safety plunger or some part of the firing mechanism.

THE CARRIAGE.

For the purpose of description, the carriage is considered as composed of the following groups: Sleigh (including recoil mechanism), cradle, trail, traveling lock, elevating mechanism, traversing mechanism, wheels, road brake, and shield.

The sleigh contains the recoil and counter-recoil mechanism and serves as a support for the howitzer, being secured to it by the breech key and the holding-down band. The recoil counter-recoil cylinders, and two air cylinders are bored in the sleigh and form the recoil mechanism. The ends of the recoil and counter-recoil cylinders are attached to the cradle and when the howitzer is fired the sleigh and howitzer recoil, sliding on the cradle sides.

The holding down band is anchored on either side to the front band clips, which are secured to the sleigh. Grooves are cut underneath the two top edges of the sleigh, and are lined with bronze liners, known as sleigh slides. These liners slide on the cradle clips and guide the howitzer during recoil. Five longitudinal cylinders are bored in the sleigh, the two upper cylinders running about one-third the length of the sleigh, forming air tanks and are closed at the front end by the air tank heads. The left air tank head is provided with an opening in which the gage-cock body is assembled. A pressure gage may be assembled through an adapter to this gage-cock for ascertaining the pressure in the counter recoil system. The gage-cock is also provided with a pointer which registers the quantity of liquid in the system on a scale provided on the air tank head. The two lower cylinders extending the full length of the sleigh, form a housing for the recoil mechanism, the right cylinder being the counter-recoil cylinder and the left the recoil cylinder. The small equalizing cylinder in the center of the sleigh, extending only a short distance, is closed at the front end with the filling valve, through which air or liquid is introduced into the system.