With your action, I'd think 28 or 30 sherman mag. You'd most likely want to do a Wyatt's box or dbm for that though to shoot the heaviest per caliber with minimal jump as a repeater if that's your thing. That being said though, I haven't had trouble getting bergers to shoot with .100 or more jump. If you want to keep the action as is bdl and keep the bullets right to the lands, I don't see anything wrong with going with any of the max or ss chamberings. With a little tuning I'm sure they'll run fine. I've got a 270 sherman long action '06 case head and a 25sst myself. They're my main go to rifles these days.