I have developed a couple of smokeless loads that I use in my Miroku 1886 (45-70). Some of them were on the upper end of energy, most of which was transferred to my shoulder. I since backed them off to approximate BP velocities. Part of the reasoning is so that I can use them in either the '86 or my Pedersoli Sharps. The velocity readings below were taken with the Sharps, which has a 32" barrel. These should be well within pressure limits for a modern '86, but why should you trust me? You don't even know who I am. I may also be a bad typist and I might have typed loads that are downright dangerous. For those reasons, PLEASE double-check everything here before you trust your rifle and your life to what I've written.
The loads below use a Lyman 457193 bullet (415 grains), Winchester brass and CCI 200 LRP.
35 grains Alliant Reloder 7. 1366 fps
35 grains IMR 4198. 1427 fps.
I have had decent accuracy with these loads, but my main target usually ends up being tin cans. The 45-70 may be a bit of overkill, but it sure is fun!
CC Griff