Just happened to see this thread, and thought I might comment. In the 80's, I bought a Ruger No. 1 in 45/70. I rechambered the barrel to 45/120. It was interesting, but not totally useful. You might want to determine the twist used in the DR barrel. I found that any heavy bullets had to be driven far out of the range of a 45/70 capability to stabilize. In the very strong Ruger, I could approach 46weatherby velocities and they stabilized. Anything less and accuracy was so-so. Even a light 458 load was marginal. With the original 45/70 twist, the combo was basically a light bullet or express load. With the 500 gr and above, only max loads worked.
I did however experiment with some reasonable shot loads in the extral long case, and they worked quite well at skeet ranges.
