Can't help with the casting / wheel weights issue. As far as loads for round balls goes, it's a personal decision. Some folks like the lite wimpy loads and some folks like me load em up :haha: . What ever load you try, I'd suggest using a wonder-wad over the powder. Uniform loading practices such as throwing the charges at home before going to the range, using the same manufacturer for the balls, caps, powder, etc. also helps. Using a loading stand to obtain the same pressure on the charges and seated balls also plays a part in the results and how well the pistol groups!
And remember that a small ring of lead gets shaved off the ball as it's being seated. My Walker uses a 50 grain charge of 3Fg Goex, an ox-yoke wonder-wad and a .454 Hornady ball. This charge for this gun is very accurate...I hit a 135 yd Gong with the thing :shocked2: . You'll find that each gun has a "sweet spot" as far as the charges go. Don't be affraid to use a little powder to get the ball to the target quicker, especially on those windy days!
Good luck and let us know how you do!
Dave