Slightly different idea for a rabbit gun, but my solution to the same problem was the .25-20 The 86 grain bullets at 1100-1300 fps do little damage to edible game and are very quiet. Mine is an older Savage 23B bolt rifle, but the .25-20 can be found in lever guns too. Almost performs like a reloada...

Shot a LOT of buckshot back in the days when running deer with dogs was legal in Texas. Each gun is a rule of it's own but "in general", a modified choke will give the best patterns with 00 buckshot, but occationally you will find a gun choked "full" that gives excellent patterns...

Just curious.......will this hunt be for lever rifles only. Could be kind of fun to see different rifles used and owned. Of course I'd have to pull a trailer to bring them all!!