IMO, bone stock, default factory setting, gun is over sprung. Mine is the same. 2100, all the way backed out was peak velocity. With CW 1/8th turn lost 3-5 fps. Went up to 2350, 22gr slugs were at 857 at 2100, at 2350 with no spring adjustment 896. With adjustment peaked at 913. ⅛turn past this, down to 904, another down to 887. Found 21gr HN shoot best anyway. 927 is plenty.
Bottle and adapter en route. Have new valve and housing on way. Going to add side mounted plenum... I'm not looking for much more power, would like to have the 21grs in 940-950 neighborhood.
Shot cycle was nicer at higher pressure with very little spring added.