I am extremely reluctant to respond, but here goes. Since this forum's inception, I have read, and used, the under- powered loads listed. Some of been so low that the bullet barely exits the barrel, if the ultra light powder charge (4198,etc) even ignites.
Fiirst of all, I have been casting (RCBS 320 GR GC), loading, and shooting a 45-60 WCF for nearly 4-years. Several thousand rounds.
The toggle-link (modern repo) is not nearly as weak as some think it is, or as strong as some want it to be. Mr. Lansing asked about 4895. I have used that powder with good results, very accurate. The best ,however, is a slightly compressed load of H4831. After 500 + rounds of that load, I have found that it is by far the most accurate and consistent of anything I have tried. Before anyone responds, check out Ken Waters Pet Loads for cast bullets in the 45-70. Interpret from there, with common sense, of course.
Powders used with best results (with consistency,pressure, and accuracy as the standards):
1. H4831
2. 5744
3. H4895 (actually tied with 5744)
4. 2015