1. My Ruger works best with a .457 or .458" size ball, not the .454". My conicals come out of the mold at .457".
2. Always seat the ball to compress the powder charge...with smaller charges, that means the ball will be well down into the cylinder. Never shoot with any space between powder and ball.
3. Some people like to use treated felt wads on top of the powder (these ae sold specific for that use)...some people like to seat the ball directly on the powder without wads. Each and an argument for why it is better and why the other guy is crazy.
4. Will grease over the top of the seated ball. tradtionally this is to guard against flash over from neighboring chambers when fired, but it keeps the fouling soft and lube the pure lead ball's passage down the bore. They sell various subsdtances for this I like the Wonder Type lubes, old timers will just use crisco.
5. Companys make two common sizes of pecussion caps, #10 and #11. My Ruger will take #11's, but only buy one tin of them until you are sure.
Now becasue of #2 above, the MINIMUM load would be how ever little powder lets the ball seat and compress it. the max. would be how ever much allows compression the powder and seating the ball below flush to allow the cylinder to turn. Can settle on anything inbetwen those two. I load mine to where the end of the ball is slightly below the end of the cylinder.
I have read that the Old Army has been tested with as much FFFFg that could be loaded and still be able to seat the ball with no problems. I would not go that far but I will say that I do not believe that there is a Stronger Percussion Revolver made anywhere than the Ruger Old Army. Personally in mine I have used nothing but good old black powder, 30 - 35 gr of FFFg and both balls and conicals. I use lube on top of all cylinders after loading, this does keep the fowling soft.