i have an old springfield 45/70 trapdoor and shoot rounds bought at the store. you should have a gunsmith inspect your rifle prior to shooting ...that's the only way to be safe.

my gunsmith told me that today's 45/70 shells are "downloaded" at the factory so they will function safely within old rifles. if you want to handload to get maximum performance would suggest buying a modern 45/70 rifle ...marlin makes some nice ones and you can find trapdoor and sharps replicas in cabellas.