Wheel weights will work for casting but because the cast balls are harder they usually need to be used with a thinner patch material.
Most pure lead balls deform a little when they are loaded and take on some of the shape of the rifling and even the shape of the patch weave.
Because the harder wheel weight balls don't do this, using the thick patch that is used with a pure lead ball will make starting and ramming the ball down the barrel harder to do.
Speaking of starting, I forgot to mention you will need a "short starter" to get the patched ball started into the muzzle.
These look like a ball with two sticks coming out of them.
The short stick (about 1/8" to 1/4" long) is used first to start the patched ball. The longer stick (2 1/2" to 3" long) is used to drive the started ball down the bore a bit.
This tends to free up the ball a bit and gives a nice deep hole to get the ram rod aligned.
Oh. While I'm writing, NEVER grab the ramrod more than a foot from the muzzle when your ramming the ball.
I know. The guys in the movies just grab the far end and give one mighty shove but that's a good way to break the ramrod and get it shoved thru your hand.
Trust me. Take several 8 to 12 inch strokes and you'll have no trouble.