I am completely confused

Decided to check my HW100 over the combro this evening to make sure all was OK.

I put some penetrators through (9.5gr) and found the power to be going a touch over 12 Ft/Lb

PANIC

Put some Bis Mags through (10.6gr) power fell to about 11.6 Lb/Ft

Put some Barracudas through (10.35gr) power drops below 11 Ft/Lb

My usual pellet - accupel (7.9gr) is getting power of around 11.6Ft/Lb

BUt AA feilds (8.44 gr) are putting me over the limit again 12.18 Lb/Ft.


So.......power is OK with heaviest and lightest pellets but is going over with mid-weight pellets

Can anyone please help explain this also any advice would be good but I guess the gun is going to have to go away to be tuned down a bit.

Cheers,
Si