I cast my own roundball and get about 16 to the pound out of a 20 gauge. I don't weigh them because I'm lazy. I was shooting out of by hunting bag because I didn't want to take my stuff over to the 100 yard range, so I just used spit. I normally use murphy's oil, alcohol, and peroxide as a lube mixed 1-2-1. Most smoothbore like a thin patch for some reason but since I shoot a .600 ball I use .015 ticken, the stuff you can get from Walmart. I just put the powder fown the barrel and patched round ball on top of it, no cards or wads. BUT !!!! that isn't to say it doesn't work. I've had good sucess with it but I'm lazy and don;t want to do the extra work in a timed event. I've had good result running a ball between a rasp to "Kurd" the ball to bore size, then use a powder, wad, ball, over card combination. The target at 100 is about a yard by yard wide, ten ring is about 2 1/2 inches. It's a 20 guage.
Shooting a round ball out of my gun is tough. The gun is light and the "hammer Shock" coming out that big Virginia lock it very noticable. You also have to really hold it tight into your shoulder. You can't shoot it like your rifle, you have to shoot it like a shotgun. Like I said earlier, smoothbore like a thin patch sometime, give it a try. Also, stay away from cleaning between shots. You can shoot a shoothbore all day without cleaning and mine shoots better dirty. Also, try a water basiced lube. That way you halfway clean the barrel everytime you load.
S'Poke