I would try a VLD type champfering tool to see if that helps just to work the brass less. The tapered expander is SOP for straight walled cases like the 45-70 especially with cast bullets. Test a case out as it is easy to over do and end up having the cartridges not chamber easily or at all, been there done that.

"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli