Threaded barrels are problematic if they are not fixed since they are meant to move upward. Adding weight to this encourages wear. Try to find out if the Airsoft Surgeon or ProG4 fixed Hi-capa/1911 barrel is compatible. I would buy exclusively over seas with this many parts/much money. Try WGC and Redwolf. My 6.01 is a 6" and gives me a pretty good pump but I think it would be around 350FPS with .2g and propane. Of course, in joules, the converted velocity increases with heavier ammo.