Sry - didn't have a Rice barrel, but did have a barrel with reverse width rifling. The grooves were very narrow with wide lands, much like original barrels. Even so, I used .311" RB's from a Lee mould, to start with, then switched to .320" from a .319" Lee mould, both with .022" to .0235" patches. It was very easy loading, oft demonstrated to Taylor on the trail, how only needing 2 fingers on the rod to seat the patched ball, whether using milk oil or water based lube. No wiping nor swabbing needed. When using mink oil, the 50th shot loaded easier than the first. I can only assume this was because the first was wiping the week-old film of WD40 down when seated and the 'oils' were not compatible. After the first, loading was noticeably easier, even though the first one was also quite easy. This barrel, like all my others, does not build fouling and never needs cleaning while shooting.
I do have a .36cal. Rice barrel. It is even easier loading, if that is possible. but I do use a .350" ball in it, along with the thick patches and short starter.
Pressing on the patched ball with the short starter knub, forms the ball into the bore. No hitting is needed. choking up on the 5/16" hickory rod will do the same thing. The starter is not needed, just handier as I've been using one since 1972.
I always use DEAD-SOFT lead, no alloys. I tried Hornady's 0 buck and it measured .320" and was too hard (3 to 5% antimony as advertized) to load easily.
The # buck might have been 00 - like I said, it measured .320"
