Air leak between cylinder head nozzle and bucking

Hi guys, I'm new to this awesome forum and have been having problems with my tsd sd700 vsr-10 imitation (same gun as well mb03). The gun shot well until recently the bb's started dropping at around 100 ft. I am 99% sure that there is an air leak because the cylinder head nozzle doesn't seem to be going far enough into the bucking, as the hop up seems to be working fine and compression on all other parts seem normal. The gun also makes a different sound when firing, as the piston seems to be smacking against the cylinder head faster, but the bb's aren't going as far. I put some .2's in the gun, and they were flying up, so I know the hop up is working fine. I also super-glued an O-ring around my cylinder head nozzle in order to fix the leak, which actually kind of worked for a few shots, but the O-ring slid out of place as expected. I recently bought a stock bar10 bucking +chamber in attempt to fix this problem, and as soon as I installed it, the gun shot perfectly for a few shots, although the bolt was harder to push forward and seemed to get stuck on something, then later had the air leak problem again, although the bolt became easier to pull forward. Does anyone here know how to make the cylinder head nozzle go further into the bucking, or to seal the leak where the cylinder head nozzle meets the bucking? Any help will be appreciated.