Regarding the power drop and shooting at 45 yards, when I received mine from bowkett , what I decided I wanted to do being a consistant shot to shot kind of person, was to fill it so that it's full then put every shot over the Chrono and count how many it does with a range of fps that I would be confident with.

And so I found that mine was shooting jsb 16grains at 11.4 straight from the first shot and gave me 35 perfect shots with a spread of just 4 feet per second, but allot were identical. So with that I looked at my metal drum with the indicator through it, and saw that once the 35 shots were shot, the inside thread would drop to being perfectly flush to the top of the drum.

Therefore I am confident that if I can see any of the indicator protruding the drum I'm good to shoot a vermin or a target in Hft with confidence that the shot is going to be regulated if you like, and believe me my one has come back better than some of my regulated pcps

I have the longer barrel on mine but have yet to measure so assume it must be a 15". If I carried on shooting which I did for another 8 shots, I would probably be able to plink for say 50 shots and wouldnt be too far away from an extra half mildot at 45 , but take my advice and put it through the Chrono as I did then you will be more confident in whats going on with yours

Atb
Daniel