Unfortunately not, the added 40fps came with the softest spring as previously it gave me 690 jsb and 670 superdome, other springs give very similar results to previous tests with maybe a +/-10fps, so nothing conclusive. I put the standard internals back in the gun yesterday to check all was ok at the breach and have actually gained 10fps from when they were removed, so am pretty sure no leaks at breach. So in short I still have to prove/disprove the piston sealing, excessive friction or something wrong with comp tube. Comp tube will be the biggest unknown as I only have one to play with. Thanks again.