I've just completed my latest project based on the Hammerli 850.
I call it my D9 rifle inspired by the District 9 prop weapons.
Quasi-bullpup with the standard electronic trigger.
36" long and 11 lbs with scope. Balanced at the front of the trigger guard.
Thanks to Rich for the 850 and the 850 Resource for the HPA conversion info.
With a 1600 psi reg, it's maxed out at 950fps w/ 7.9gn pellets.
It may become my FT rifle. I can't wait to shoot it.
EDIT: I bumped the pressure up to 1800psi and drilled out the adapter.
Now I'm at 1000fps w/ 8.4gn.
It's just plain cool.