Out of a 32" barrled H&R Buffalo Classic:
16.5 gr gives a velocity of 1600 fps +/- 20.
10.1 gr gives a vleocity of 1195 fps +/- 5.
Might try lower loads some time, but the 10.1 produced a 50 yard offhand 3 shot group that was an upside down Mickey Mouse, the bottom two a little closer and it would be a cloverleaf. 1600 fps load shot more of a pattern than a group, didn't even bother trying to measure.