Well I was using Remington brass. But since that bullet has no cannelure, I didn't consider crimping, as the ammo was for a single-shot rifle anyway. But some people like to crimp. However, I ran an experiment once using a case full of IMR 4064 in the .450 Alaskan loading for the Winchester Model 71 lever action. I used a small expenadeer button instead of crimping, just letting case neck tension keep the bullets from moving forward under recoil and the powder charge preventing the bullets from going deeper into the case. It worked perfectly in the .450 AK. I don't know if .45/70 cases are thick enough to have enough case neck tension to work this way, and of course, if the powder is TOO compressed, it will push the bullets back out somewhat after you seat them, increasing the overall loaded length of the round. This is a no-no in a lever gun.

You might try IMR 4198-it takes less of it to get the same results you get with IMR 3031. In addition, Alliant RL-7 might work, and it is denser and takes up less space in the case than 3031 does. I've had some good results with RL-7 in the .45/70.