Dong Ki M1 Carbine from Korea.

A rather unique rifle.

It is a .177 single-shot,spring/piston powered,side-lever cocking weapon. You can see the opening of the loading port halfway down the top-wood.As the cocking arm swings outwards a rotary breech presents itself to the loading port.Drop a pellet in then close the side-lever.You are now ready to shoot. MV 850fps. 

Top-wood removed and cocking arm retracted.The "snout"of the sliding cylinder has an "O" ring that seals against the side of the breech-end of the barrel. 

 Simple effective lever system opens the rotating loading tap.