Finished my HPA conversion on the RWS/Hammerli 850. I got the kit from the850store.com. It's now shooting JSB 8.4 grain pellets at 1029fps - giving 19.75 fpe. And shoots about as well as before the conversion (not enough time yet to really evaluate, but looking good). Provides 60 shots before the pressure in the reservoir goes below the output regulator pressure - at that point, pressure has fallen from 3000psi to about 1600-1700. Also did the coat hanger wire - trigger mod (yeah, I know it sounds cheesy, but it WORKS - and is not that difficult to do). Heavier pellets boost the output to about 20.78 fpe (10.5 grains at 943 fps).