For best accuracy with an Air Wolf, definitely load pellets using the single shot tray, no magazine. The newer Red Wolf shoots better with a magazine, but again accuracy is notably better using the single shot tray. All four FX rifles I own and all FX rifles I have shot, do very well using a magazine.
STO - Even more odd; that all four of my FX rifles shoot REALLY well using the magazines. And I have shot them a lot.
I have talked to people in Field Target competitions who stopped using a magazine in their Air Arms rifles due to accuracy issues. It always bothers me to hear of such inconsistencies among rifles, regardless of the brand.