Colin, might I suggest, that it's easier to load a nice tight, accurate round ball with a smoother crown. As with the machined crown and while the barrel is still in the lathe, simply holding some emery or wet/dry smooths against the cut crown polishes and radiuses the it, making starting the patched ball so much easier.

These really small bores seem to benefit from very tight combinations, to the point where a lot of guys use bore size, or slightly larger than bore size balls with .018" or thicker patches.

That requires a very smoothly radiused crown to avoid cutting the patch when seating the ball into the rifling at the muzzle.

This is the muzzle on that squirrel rifle. I use a .319" mold that casts .320". I like to use it with a .0215" ticking patch. The .311" ball was also fairly accurate, but liked a thicker .023 red/white/lt.blue/dk.blue mattress ticking patch.