I just shot it over the chrony starting with a 2200 PSI fill.
The velocity with Kings started at 735FPS, after perhaps 20 shots it went up to 807 and then started going back down, this is 100 FPS lower than before.
When I got the rifle it was doing 975 FPS with a 2800 PSI fill...
So I shortened the spring to slow it down. Which put me at 935 or so. I think the spring has been compromised due to shortening it, it is just not opening up that valve up.
Now on the air leak. I put painters tape on the area where the poly tube goes from the lower to the upper on both sides, I put it on the cocking slot and I put it on the hole on the rear of the reciever where the safety was.
When I shot it only the tape at the cocking slot was disturbed and then only slightly. If I put my fingers ont hat slot when firing, I feel a slight air pulse. So perhaps I am only experiencing the air displacement from the hammer movement?