Having a front cover, a handle and a native sear, I decided to pile a full-fledged gun with a 12mm stainless barrel and a stainless receiver! Piston combined caprolon + titanium with one O-ring and a segment valve for pumping through the barrel with a pumping piston! As a centering of the piston in the barrel applied a split bushing of graphite-filled kaprolon! Excessive backlash of the piston when arming the platoon removed the length of the piston skirt in which to facilitate the hole made longitudinal! Backlash became 1.5mm! In general, nothing new except a split bushing of the piston and a split bushing in which the piston is fixed with a sear for centering the piston skirt!