.... and welcome. You would need to tell us the calibre and what pellet it is in order to be able to answer that one. Heavy pellets are slower than light ones .. sometimes by quite a margin.
Mark
S410C .177 Regged - MTC Viper 4-16 x 50 S410K .177 Regged - Hawke Nite-Eye 4-16 x 50 AO IR S410K .22 - Hawke Sport HD 3-9 x 50 AO IR Logun Mk1 .22 - AGS 3-9 x 40 Theoben Taunus .22 - Simmons 4-12 x 40 AO BW1911R2 Walther CP99 Webley Premier .22
With 8.4gn AA fields at around 11.4 fpe it wiil be in the 770's fps
Air Arms s510 .177 MTC Mamba Lite 4-16x44 Air Arms s510 .22 MTC Mamba Lite 4-16x44 with diy NV Air Arms TX200 Mk3 177 Full WD Tune Zeiss Conquest 3.5-10x44 HW99s .22 Full WD Tune Vortex Diamondback 2-7x35