have you got Hawke Chair Gun software. Run through the figs with your chosen pellet, speed and true scope height - nominally centre of bore to centre of scope tube but ideally you would check scope height by shooting at a mark on paper at very close quarters couple of ft max and measuring POI to sight mark (may need a pin hole lense cap to focus that close)
Also have you centred your scope as per the BFTA guide - using a couple of v blocks etc. All may help to find if you have an issue
FTP900 +Sightron S111 10-50 x 55
AA Pro Target in FWB FP70 stock + MTC Mamba lite
Daystate Airwolf + Bushnell Elite 6500
" life is about the memories we hold and not the things that we own"