Upon recoil to the right, piston 2, whose rod 1 is attached to the barrel, compresses the air in cylinder 3. Upon counterrecoil, the compressed air, acting on the piston, returns the barrel to its initial position. Leakage of air from the cylinder is prevented by delivering fluid to the seals of the counterrecoil mechanism at a pressure somewhat exceeding that of the air compressed in the mechanism. Fluid is delivered from intensifier 5 having piston 4, with different effective areas on its two ends. Air is at the right end of piston 4 and fluid at the left. The right end of the intensifier cylinder is connected to cylinder 3.
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