Ran some .32-20 chronograph data today, the 8.3 of Alliant #2400 is a bit warm in the Colt Police Positive, so I'd recommend cutting to 8 grains even. With 31-100T (earlier bullet) unsized at .312 diameter velocity was 916 fps from 5" Colt, Sd 56, ES 128. Ballistic uniformity may improve with bullet which fits throats and heavier crimp, but this load shot to sights at 100 yards and was accurate.
10 grs. IMR4227 with 31-114D gave 962 fps, 27Sd, 62 ES, also shot to sights at 100 yards.
10 grs. IMR4227 with 31-105T 985 fps, 25 Sd, 61 ES.
3 grains Bullseye with 31-114D gave 741 fps, 35 Sd, 92 ES. Mild compared to factory, Could stand more powder, believe that 3.2-3.3 of Alliant Bullseye should be fine, but not more.
Various trials with IMR4198 were very mild, got vertical stringing, lots of unburned powder in revolver. 12.5 grs. with 31-114D shot OK in rifle, approximates factory velocity 1248 fps.36 Sd, 114 ES. Increasing load to compress charge as if loading black powder may help rifle uniformity. I don't recommend using 4198 in the .32-20 for revolver use.
Factory ammos fired for reference:
Factory Rem-UMC "Dogbone" logo box, from 1930s, Sharpeshooter powder 898 fps, 44 Sd, 116 ES in Colt, in Savage sporter rifle 1302, 15 Sd 36 ES. 3" group at 100 yards rifle with open sights.
Old WRA red & yellow box 100-grain lead, Infallible powder, 870 fps, 28 Sd, 71 ES in Colt, in Savage Sporter rifle 1263 fps, 28 Sd, 93 ES.
Modern W-W 4.5 grains of what sure looks like WST 100-grain lead 778 fps, 27 Sd, 69 ES in Colt, in rifle 1172, 18 Sd, 55 ES
Modern R-P 100-grain lead, 3 grs of fine black granular like .22 LR powder, 780 fps, 11 Sd, 49 ES, in rifle 1150 fps, 44 Sd, 137 ES
73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia