My CVA .45 calibure "Kentucky" rifle was most accurate with 70 to 120 grains Fg or Pyrodex CTG behind a patched .440 round ball.
To work up the most accurate load for your particular rifle, load start with 1 grain of powder per calibure and work your way up.
If your rifle is in good condition (bore, and breachplug, nipple, and drum threads) are not rusty, you can safely go as high as 2 grains per calibure using FFFg, or 2.5 grains per calibure with FFg, and 3 grains per calibure with Fg.
Also, try FFFg, FFg, and Fg when working up your loads, and vary the patch thickness.
Some .45 rifles do best with a .440 round ball and a .15 patch, others may do best with a .20 patch, or even a .445 round ball and a .15 or .20 patch.
My particular rifle "couldn't hit the broadside of a barn -- from inside the barn" with FFFg and a patched .440 round ball. With FFg or Fg I could (and did) shoot broomsticks in half at 100 yards.
(Easy shot. A 1 inch broom stick at 100 yards looks the same width as the front sight blade. You just have to line them up.)