Fx mavrick tuning hammer screw

Fx mav 22cal So i upgraded hammer to meduim weight hammper spring tunned it to 960fps at it would vary around 9 fps
which was perfect I was fine with tht..

NOW i tried going up to 1000 i did and it was tuned poopty accuracy so i went back down but i cant get the fps to stabalize it keeps bouncing so ill shoot 10 shots and the will vary from 970 to 930 which is poop NEED HELP PLS
 
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best shot sting i got for now need help