Hi, I've got 2 rifles in .20, a MK 1 Rapid and a Huntsman Classic, both are fed a diet on H&N FTT weighing 11.4 gr, which i find are the ideal weight for .20 in sub 12ftlb.
However, not all barrels like them.
There are heavier pellets, the Daystate and JSB at around 13.7 gr. but to me that's defeating the object, you might as well stick with .22.
There is a light pellet in .22, Falcon Accuracy at 13.4 gr which i use or my .22's.
Regards,
Tinnie56