OK two more springs 244 mm x 40 lb/inch and 255 x 34 both cocked spring force around 185 lb. No weight give 7.5 +/- fpe so a little lower than first trial.
Still fairly flat across pellets. Slightly lower Bisley 10.2 tho' now.
Edit. Sorry got my thong in a twist. Revised figures above. The 255/244 with weight gave 8.5.
Shedtuner! Thanks for the info. Going to start TP at 2.5 and work up if need be. What does "my PE" mean please? Assumed personal experience but have learned not to assume.