My fps/fpe numbers won't help you much cuz I'm at high altitude but mine does 8.5fpe with a full power Macarri kit. I can tell you it didn't like anything heavier than 8.44jsb (more harsh shot cycle above 8.44 gr) but prefers 7.87, and before that shot a couple thousand of the boxed 7.9gr crosman premiers. So, it seems to like midweight pellets.
My general opinion of the gun might be of use though. It's a great springer. I had both the HW77k with the laminate stock and the 50s-I kept the 50s.
The hold sensitivity of the 50s is very low compared to the 77k, making the 50s much easier to shoot. I also like the lighter weight and more compact size of the 50s over the 77k.
I always hear about how hard the model HW50s is to cock, I haven't ever thought it was hard to cock. In fact, I think the articulated cocking arm that was mentioned above is what makes the gun special. It doesn't have the typical stock fork screws at 180 degrees to each other like you see on most break-barrels. For stock fixing, It just has one big lug screw on the bottom of the forearm and a smaller screw in the trigger guard. Something about that configuration makes the gun not require loktite, nor does it develop a wandering poi problem like I've seen with typical stock screws through the fork. My guess is that the thin wood on a break barrel stock fork that the screws would regularly go through, are subject to swelling and flexing through humidity/temp changes, which equates to shifting poi and screws that won't stay tight.
Anyway, if you decide to get one and intend to do any target work with it, you owe it to yourself to look into a barrel sleeve from Tinbum in England. It makes the gun about a pound heavier but even easier to shoot accurately. Mine, well broken-in, with the JM kit and Tinbum barrel weight/sleeve makes it almost as easy to shoot accurately as a recoilless FWB 300s.
