Upon recoil of the barrel, rod 1 with piston 2, linked to the barrel, moves to the right, forcing fluid from cylinder 3 through throttle valve 5 into tank 4. As recoil ends, air compressed in tank 4 forces the fluid back into cylinder 3. At this, piston 2 is moved to the left by the fluid effecting counterrecoil of the barrel. The opening in the throttle can be changed, thereby varying the velocity of motion of the barrel.
$3775$SHP,FD$