A mate bought the above Hatsan and wants to know what pellets they generally like... i suppose heavies as its not tuned/tamed...
I would suggest JSB heavies.
Best would be to convince him to have it down tuned, he will enjoy it much more.
Can also try H&N Baracuda Match 10.65gr.
They were pretty good in my HW77K before it was tuned for FT. I little heavy now!