those guns are the ultimate "tinkerers" toy. I have built a couple now. The one in the picture has a bolt by Roy @ Mountain Air, Crosman Steel breach (long), light valve return spring, standard hammer spring, hammer spring adjuster by Art @ ArtShack.com, the valve was opened up considerably for volume, port angled, polished, ice maker tubing transfer port. The stock was a deal I cut at Steve Corcoran's place during Christmas break from a nice walnut blank I got from Boyds. I used his machines and his patterns, but I cut and finished it myself.....best Christmas bonerus ever!!!! I did a simple trigger parts polish and added a trigger shoe a la Crosman. Funny, I never even chronied it,....because......it was so freakin' cold here in Texas my CO2 guns shot miserable....hence, why I sold it....Amen! Didn't mention the carbon fiber and aluminum muzzle brake on that devil by LarryR.........phew, why did I sell that one again....oh yea, the cold CO2:)