I have a Maxus Sporting 30" Carbon Fiber in 3" , love the gun and the way it handles because it has a flat rib and flatter
finish than a SBE II
I've had no problems with the spring in the piston but , I traded for a sealed piston just to see
how much of a difference it would make ( NON ) as far as the way it operates ,but , it does shoot cleaner as I've run 450
target loads through it in one day and all I had to do was , wipe the piston down and put a drop of Miltec oil on it .