Craig,
I've used Unique for handloading the 45-70. It is relatively inexpensive and reasonably accurate. I've always used some dacron wadding to hold the powder against the base of the cartridge for better ignition because the case has so much empty space with that little bit of Unique. Don't have my records handy but somewhere around 13 grains...you'll have to tweek your own load.
I don't use Unique any more because I'm leary of double charging the case, that's real easy to do and a little Unique goes a long way. A double charge (26 gr) could be a bomb. Lately I've had some success with a 405 grain cast bullet and 38 grains of IMR 3031, with a tuft of dacron. This is not a maximum load, kind of mid range and nice to the shoulder but accurate. I have noticed less ledding problems when I add a bit of dacron, not sure why, but it works for me.
Roudy