Noting that the original post said "Reb Navy" I assume it is a brass framed pistol.
If this is true, it would be a good idea to keep the powder loads on the light side like 20-25 grains of powder.
Because the chamber is very likely to be capable of holding 28-30 grains of powder plus the ball these light loads will result in the ball needing to be rammed quite a ways down.
Many have found that having the ball close to the chamber mouth gives better accuracy but remembering that it is necessary to have the powder compressed a bit raises a problem.
The answer to the problem is to take some corn meal, cream of wheat, grits or something similar along. Then after pouring the powder into the chamber you add the filler until it is about 3/8 of an inch below the chambers mouth.
When the .45 diameter ball is rammed flush to slightly below the mouth of the chamber the powder will be compressed and the gun should shoot at its best.