Joe, you are correct, there isn't any substitute for a big cast bullet when it comes to thumping critters.
For load data, if you have a good hard cast bullet with a gas check, you can start with any reputable source of jacketed data, and work up. There are sections in many of the reloading manuals for Marlin and Win lever guns, that are loaded to pressures higher than the SAAMI spec for black-powder .45-70s.
Odds are that your shoulder will give out long before you get into pressure trouble!
Be sure to clean all the copper out of your barrel before starting. Good luck and let us know how it goes. Yes, gas-checked bullets will help prevent fouling and in general, make it easier to work up loads.
For load data, if you have a good hard cast bullet with a gas check, you can start with any reputable source of jacketed data, and work up. There are sections in many of the reloading manuals for Marlin and Win lever guns, that are loaded to pressures higher than the SAAMI spec for black-powder .45-70s.
Odds are that your shoulder will give out long before you get into pressure trouble!
Be sure to clean all the copper out of your barrel before starting. Good luck and let us know how it goes. Yes, gas-checked bullets will help prevent fouling and in general, make it easier to work up loads.