There are ,many things that all together make good shooting ,good fundamentals are a must as are good ammo, good sights , and good practice what ammo are you shooting? how much do you practice? the best practice for that type of shooting is a 6 or 8 inch gong and start at 50 yards all offhand practice bringing the rifle up to your shoulder while taking the safety off when the gun goes back down to ready position safety back on then fire at that gong ring it step back 15 paces repeat,kneel fire repeat go through the whole sequence each time then 100,150. 200, etc as far as you want to shoot . but you must have the same ammo you will hunt with so everything works together.
Belt fed is correct those Kentucky long rifles are made for round ball only patched lubed and pillow ticking is a great patch material I have killed deer bear elk all with a 50 cal and real black powder not the fake crap,the long sight radius is what makes those long guns so accurate I used to shoot 30 to 40 lbs of black powder a year in matches out to 200 yards and have had many groups in the 1 inch to 2 inch size at 200 they can be very very accurate....