yeah that was the arnies link i was on about.
out of interest, when you have yours apart to change the o-ring might be interesting to see if the piston head has any vents?
if not, a possible modification there to get a good seal without a super tight o-ring, i have something similar going on in the makarov and it works surprisingly well (as in it'll cycle on noticably low amounts of gas)
damnit, this is making me want to get one again.....