while running cartridges,and looks almost stock(no tube extension)
Put in a delrin head valve,shaped to the minimum OD at the valve seat ,larger at the spring end.I don't shim the spring,and get well into the 800's on co2 with .22 crosman premiers with this setup.A .047" wire probe,as long as will work, is part of the high output setup,as is careful work in the port bend,and an oval or dual port in the barrel.With the ultralight striker you'll get 30-40 shots on a fill even at this high an output(if you get the valve head to valve body clearance just right)
I've got an even more radical striker and valve body I haven't tested yet,but you get the idea from the pics.
