just stripped,cleaned and regreased it ,I dont have a replacement for the itsy bitsy teeny weeny O,ring at the bottom of the piston, but when i aired up there was no leak, dry fired a few times ,got a metalic clicky noise when firing a couple of times (like the piston isnt re-sitting properly and then clicking into place due to pressure) got some leakage again then when I vented the marker and asa no more leaky..think it means this o ring is buggered ....who sells Guerrilla service kits in the UK ...or does anyone service the regs?.
I also noticed that the bottom of the piston looks like it has been scraping against the brass bit in th ebottom of the chassis...