That's a helluva powerful springer for .177. That powerplant is better suited for .22s.
I have a 177 Diana 48 and it would be better off if it was a .22.
I only paid $70.00 for it at a pawn shop. Where else would I find a 48 for that little money?
Stay away from the lead-free lightweight pellets, like the Crapo, I mean Gamo PBA pellets.
They're not good for your spring or piston seal.
You may even want to tune that 350 down to a little LESS power.
The more powerful the springer, the harder it is to get good groups and the more crucial it is to use the perfect springer hold.
I'm not selling any of my springers, but I don't shoot them much anymore, since I got my Benjamin Marauder.