i think its gonna be a complete bugger to remove the jaws from the end of the comp tube [looking at mine] ....... but fear not, there is an easy fix
take the gun apart so that you have just the action in your hands.
degrease the insides THOROUGHLY ...
get a chopstick or similar and put a small blob of bluetac on the end of it..
poke chopstick inside the action and place bluetac over transfer port hole..[poke around the edges a bit to make sure the hole is nicely sealed]
now take your piston and de-grease that too......
put it inside the action and push it down with something made of wood [so as not to harm any metalwork].
if there is a leak you will now hear it escaping from the perimiter of the jaw-piece
if no leak, check the barrel locks up ok, and check breech seal
if it DOES leak heres the fix........

remove piston again [bluetac will come unstuck due to vacume created]
re-fit bluetac
get some threadlock and pour a teaspoon full into the action as you hold the action vertical. [try to drop it at the bottom so it doesnt contaminate the walls of the cylinder]
now put the piston back inside.
push down as hard as you can on the piston [keeping the action upright to ensure the locktight will be around the entire circumference of the jwa-piece internally]
keep pushing as hard as you can [this will force threadlock into any and all gaps ]
after a minute or so you should see a dribble of locktight coming out of the joint [on the outside of the comp tube/jaw piece]
now you can stop pushing on the piston
keep the action upright / vertical
remove piston and clean again [just incase any locktight got onto the seal]
as you removed it the bluetac will have come unstuck again, time to remove it and thouroughly clean out ALL the locktight........
when its nice and clean, do it again [poke tissue in there and use a long thin bit of wood or similar to rotate the tissue]
make sure all [and i mean all] the excess locktight has been mopped up
now clean any dribbles of locktight from the outside
leave the action [still propped upright] overnight to harden...
rebuild the gun, and enjoy a leak-free shooting experiance