If memory serves me right 3031 is on the slow side for the 45-70 and would normally give pretty low pressures even with a pretty full case. I've had light loads of h322 fail to go off in 45-70 because it was too far away from the primer in 4570. I would say there most likely isn't a problem with your powder but perhaps your choice of a really light load. I wouldn't condem it because of what happened in that instance.
