I'm not real up on modern style muzzle loaders, but IIRC, the Savage was "OK to use with smokeless powders". Once I read the blurb on the lawsuit, I had this vision of some nimrod pouring smokeless rifle powder into a black powder volume measure.
The other thing is the old myth that you can't over load a rifle with black powder. WAAAAY back when, the outfit I worked for also sold Green Mountain rifle barrels. Took a call one day from a disgruntled customer who'd suffered a split barrel. Told him to send it back, we looked at it and called Green Mountain. They indicated no big deal, the gun drills occasionally wandered and created thin spots and sent a replacement.
When I called the guy to tell him the new barrel was on it's way, I asked what his load was. Don't recall, but he said he developed it by shooting over snow and loading until he saw unburned powder on the snow, cause you can't over load with black powder, it just blows the stuff it can't burn out the muzzle. Blew my mind. Flagged his file and when he blew the second barrel we told him TS.
I've got a .50 Hawken and with that original style butt plate, my standard load is 80 grs. I did 90 once. Maybe with sabot loads the recoil would be easier, but I go with the big chunk of lead.