Different constructions of breech block are known which are to be incorporated in pneumatic devices. One such known device for expelling spherical pellets, as described in Author's Certificate No. 1 725 064 A1-SU, comprises a housing having cylindrical bore, in which a step-formed piston is placed. The rear part of said piston is wider, and the diameter of its front part is equal to the diameter of the barrel. A spring placed onto the barrel presses the piston to the rear end of the cylinder. The operation of said breech block is the follows: when supplying a certain portion of carbon dioxide (CO2) from a reservoir of compressed fluid, said fluid acts on the piston pushing it towards for compressing the spring. During that movement the piston clamps a spherical pellet from the magazine and keeps on its movement until its rear part passes through a bore formed in the cylinder where part of the gases is discharged. These gases are discharged through a specially designed for that purpose pipeline or opening in the housing, said opening being located before the front end the piston, whose diameter is smaller. The spherical pellets are expelled through an outlet in the barrel. After the shot the piston is pushed back to its initial position because of the action of the spring.
The pneumatic device described above has a complicated for manufacturing construction including elaboration of a system of channels providing a by-pass connection. Besides, the device has a significant fluid consumption for shooting away of a single pellet because of the long stroke of the piston. Other drawback is that the pressure of the fluid decreases because of the presence of said by-pass connection in the barrel.
Therefore it is object of the present invention to provide a breech block for a pneumatic weapon which has a simplified construction and more effective operation in long-term usage with minimum fluid consumption for one shot.