WENDY J, sorry for the tardive reply. I know that Reloder7 works in .45-70, but I'm not certain how well it works over a wide range of projectile weights. The thing about the .45-70 is, propellants as different as Unique and IMR-4320 seem to give anywhere from acceptable to outstanding results.
I should have been more persistent about learning of your current propellant inventory. I found some other loads, worked up in a Winchester 1886, which may give you some guidance:
18.0-20.0/Unique/300 Cast: 1500 - 1680 f/s from a 26" barrel
30.0-33.0/ 2400 /300 Jacketed: @ 1600 f/s "
32.0-37.0/ 4227 /300 Jacketed: " "
14.0-17.0/Unique/350-400 Cast: 1200-1350 f/s "
22.0-32.0/ 2400 / " " " 1200-1700 f/s "
30.0-35.0/ 4227 / " " " 1300-1700 f/s "
If using cast data for jacketed bullets, I'D be inclined to reduce max loads by no more than 10%, to avoid sticking a jacketed projectile in the bore. Those more familiar with reloading .45-70 (I've reloaded 5 or 6 boxes) may have a more informed opinion on the matter.