MC-51 1970s recoilless air pistol
With thanks to John G for this information. In Airgun Collector issue 3, he wrote: "By the 1970s attention became directed towards developing air pistols for international competition shooting, and in particular a rival to the highly successful German FWB 65 pistol was sought. A highly innovative spring air pistol was developed by G.M. Achkasov at the Central Design and Research Bureau for Sporting and Hunting Weapons, based in Tula. He combined the cylinder-in-butt principle of the Walther LP53 with a unique recoilless floating cylinder concept to produce a pistol that had a longer barrel than the FWB 65 (23 cm compared to 15.5 cm) and yet was shorter in overall length (33 cm, as oppose to 42 cm). This recoilless pistol was named the MC-51.
"In contrast to the sledge system of the FWB 65 and the opposing pistons of the Diana Giss system, recoil is reduced by the piston and the cylinder moving in opposite directions. It is not clear from the few known images of this pistol how the spring compression stage is actually achieved, which of course will require considerable leverage, as no cocking lever can be discerned. However, from a published cross sectional diagram (Fig. 8) it is evident that a back-strap lever is concealed in the grip, which drops down and can then be forced upwards to compress the spring.
"Apparently the recoilless action worked perfectly and very little recoil could be felt by the shooter. However, in order to achieve an acceptable muzzle velocity it was necessary to use a powerful spring and it was reported that target shooters found that the gun placed too much strain on their wrists after prolonged use. It is also obvious from the sectional diagram that realisation of the sliding cylinder principle required considerable constructional complexity. So in view of these factors it is not surprising that the pistol was not produced in any significant numbers as a match pistol and was soon superseded by single stroke pneumatic designs."
The principle of the floating cylinder used in the MC-51 pistol
(a) The pistol in the uncocked state.
(b) the whole cylinder unit containing the piston and spring is pulled down out of the grip, and at the same time the breech is opened so that a pellet can be inserted.
(c) The cylinder is then forced back into the grip while the piston is held back by a sear, resulting in the spring being compressed. The breech is now sealed and the gun is cocked and ready to fire.
On discharge the piston and cylinder simultaneously move in opposite directions to compress the air and propel the pellet, and the pistol returns to state (a).