Sorry, I do not have any info or experience with the Rice barrels.
For all the Forsythe barrels we used, I got the 20 bore through 12 bore from Bill Moody. The outsides were a little rough, but the rifling was great. As Forsythe stated in his book, he liked either 1:104 or 1:144 twist. The 12-20 bore barrels had eight lands and grooves with a 3:1 ratio on width, the grooves being the wider. They were .006 deep, again as per Forsythe's specs. I am sorry to say, I had heard that Moody has stopped making barrels.
For our big bore guns, we use Oregon Rifle Barrel Co./The Gun Works barrels. The 8 and 4 bore guns were all rifled at 1:144, .009 deep, everything else the same.
One of the 12 bore guns we built I kept for my own. It was almost uncanny how well it shot. And the power - oh my goodness. It was incredible how hard a hitting gun that was. Of course, like an idiot, I sold that.
John