The answer to your question is simple, but somewhat detailed. Many people have exactly the same problem you describe with exactly the same powders. The underlying reason for this is the expansion ratio of the 45-70 and it's operating pressures simply don't alow powders of the speeds you are working with to develop enough pressure to burn cleanly. Expansion ratio is simply the volume of the bore divided by the volume of the case. When we fire a cartridge, the bullet moves. (sorry for being so obvious) as the bullet moves the volume the burning gases have to fill also increases. The greater the volume, the faster the pressure drops. Most smokless powders burn best at pressures at and aboove 40,000 PSI. Most 45-70 loadings are only generating 18,000 to 30,000 PSI. A few are hotter, but not enjoyable in a rifle as light as the Handi. I would suggest that you find a load that shoots good and forget about the unburned powder, there is little to be done about it. You might try magnum primers, and yes you can try crimping as well, but neither will solve the problem as the problem is one of operating pressure, the nature of smokeless powders and expansion ratio. I have found that even 2400 does not burn cleanly in the 45-70, so switching to faster powders may not solve this for you. Good shooting, JP.
