Fx Impact performance.

FX Impact
JSB King .25 25.39gr
On max power
Max 949
Min 939
Avg 942
On 3power
Max 929
Min 918
Avg 924
On 2 power
Max 899
Min 880 
Avg 893
On min power
Max 801
Min 770
Avg 790

JSB King Heavy .25 33.95gr
On max power
Max 865 40 zero
Min 854. 50 1/2
Avg 858. 60 1.0
On 3 power
Max 806
Min 789
Avg 797
On min power
Max 690
Min 677
Avg 684
I get my best results not on max power
 
On .30 cal, 44 gr JSBs I got 915-930 on max power with one mark hotter than factory setting on the transfer port adjuster. I did not test for accuracy there and have not experimented with any other adjustments than the gun came with. I got around 90-100 shots(at least 6 magazines) on the first bottle of air(#5 spring setting) before it came off the factory reg setting of 140 bar. I did accidently over fill it to what I had in my fill bottle, about 4400 PSI. FYI, Probably the most shots on a fill with a .30 cal ever. Doesn't appear to have hurt anything, although probably not good for the bottle. 
 
I can get out average 43 shots per fill with jsb 3.25 g/ 50 grains. Average mv is 251.4 mps. It's 824.8 fps. It's about 103 joules. So to achieve performance stated by fx I miss 10 mps or 30 fps. 

Any ideas where to find missing power? 

Every setting is maxed out. Hammer spring is regulated as Ernest showed some time ago in his video.