I just go my 52 (dressed up 48) and am using Gamo Hunters at the moment. THe reason I am using them is those are the heaviest I could find at out nearby sporting good store. They weigh in at 7.5 grains even though they are advertised to weigh 8.3 grains. When I use these up I am going to get the Crossman Premier lights (8.+) and heavies (10.+) to see if I can close my groupings up.
Bottom line, you have to experiment with various brands until you find the one your rifle likes. This is the same process I go through when setting up a new .22 rimfire.