I had a Scout .50 pistol. I used the T/C brand lead conicals and it worked fine.
My hunting load was 80gr of Pyrodex and a 325-350gr conical. I've used up to 100grs but that was just to see what recoil was like. They took the prototype pistol and wen hunting in Africa with it and tested it on Impala and other animals and it worked great. I saw a video where a dude shot a spike buck with it and after the smoke cleared the deer was down and out with one shot.
Round balls probaly need some type of sabot to to make them longer as the pistol has a fast twist of rifling (1:20). The conicals loaded easier and seemed to be more accurate not to mention more knockdown power with a heavier weight.
The T/C Scout pistol was designed as a hunting pistol and will take the same moderate charges as the rifle. I think you are probably wasting powder and increasing recoil past 80grs of powder unless you had a longer barrel and 80grs had plenty of umphh for deer/black bear hunting. If you use 777, decrease the volume weight and 60-65grs should be plenty and give 80gr Pyrodex equivalent velocities and be more comfortable to shoot.
I have a Traditions Buckhunter inline pistol in .54 and max charges for it were around 80grs of Pyrodex. This pistol is lighter than the Scout so recoil becomes more of a problem with heavier charges. ITs made to take the same moderate charges for Traditions inline rifles. By moderate charges I mean using the old standard of 100-110grs used to be max load for hunting loads and then they started trying to make bean rifles out of them with 150grs charges and .357bullets in 45 sabots to get 2600fps and 300yard effective range out of a sport that supposed to have just a little more range than Archery and provide an extra season.
Here in LA., you can just about not give away a blackpowder rifle since they turned black powder season into Primitive weapons season and now u can use a NEF singleshot 45-70, 444, 44mag, 38-55, or even 500 S&W for hunting now.
If you want some deals on blackpowder weapons for cheap try looking at this page and you can ship blackpowder rifles without an FFL to your doorstep.
www.louisianasportsman.com Look in the classifieds and then browse and look for guns in the hunting section.
You can post an ad there also if you are looking for a particular rifle.
Not many want to even shoot a blackpowder rifle now that you can use a singleshot and I myself use an NEF 45-70 using either the Hornady Leverevolutions for a 200yard zero or I load a Remington 405gr JSP to around 1650fps for a moderate load but lots more powerful than the Remington 405gr factory load.