Years ago I bought a Renegade in .54 caliber. The best source for roundball at that time was to cast your own. So being new to the sport the person at the sporting goods told me the rifle took a .535 roundball. I casted up a couple hundred of them. First day on the range with the new cast ball, my friend (who had a .54 caliber T/C Hawkins) and I were beating the things down the bore with a club, and ramming trees, they loaded so tight. Needless to say we fired one roundball out of the rifle.
They did make good sling shot ammo for the wrist rocket though.

I know the frustration you must be feeling. Looks like you have some weighing to do with a scale.