I know your asking for smokeless loads.....Pardon me for being a buzz kill
Why not just use Black powder or a sub.....Why not....Your not going to suddenly make your rifle shoot any better with smokeless rounds it was never intended to shoot.
Just use black, a sub or hang it on the wall unless your a uber re-loader with so many skills you wouldn't even ask this question in the first place.
I'm not trying to be rude or disrespectful, I'm always happy to see another old snider shooting again...OK...But why even attempt to push it "even accidentally

" -beyond- what it was intended to do armory fresh..
Be easy on your ANTIQUE Snider service rifle and she will be still shooting in another 150 years.."That AND you don't have a rifle fail while your holding it

"
This is my 3 bander Really as Canadian as any firearm could possibly get..Fought Indians, brought criminals in and maybe popped a Fenian or 2
All that and you do know all us "lowly" Canadians did quite well in shooting competitions against the Brits with the "now" rare and well made II * rifles which only 650 were assembled...