I have a Diana 48 and it likes JSB 8.4 gr, RWS 8.3 gr, and Air Arms 8.44 grain pellets (all are domed pellets). The JSB;s are the best, However, I can use the other two brands with confidence. The crosman pellets are fun to plink with, but I will not use them when accuracy is inportant.
You can order pellets from Pyramid Air with the forth tin free which more or less pays for the shipping.
Let us know which pellets work best in your gun.