I've only tried 777 loose, pyrodex pellets and Black Mag. My best results have been with the 777 loose.
I live in Montana which allows sabots only in areas where a rifle could be used and in "weapons restricted areas" pure lead projectiles must be used. My best results to date have been:
250 gr Hornady XTP / MMP black sabots with 110 gr 777 loose
group = 1.5 in at 100 yds
vel average 2100 fps
260 gr dead center with 110 gr 777 loose
group = 1.3 in at 100 yds
vel average 2066 fps
I'm also going to try 300 gr Hornady XTPs in the near future.
for pure lead I've tried Hornady Great Plains at 385 gr and Ultimate Conicals at 390 gr, best to date:
390 gr ultimate conicals with 90 gr 777 loose
group = 2.25 in at 100 yds
did not chronograph