Originally Posted by
Shed tuner
if it's not the length of the guides it may well be the centralisation of the rod in the piston - is it centred correctly ? Also is the rear guide "brim" OD the full size of the main tube of the gun, thereby preventing it from moving off centre ? Also look at the trigger block - does the lead into the hole in the trigger block through which the piston rod passes show any signs of being hit / metal contact ?