It’s an obscure round, and the platforms in which it was offered were extremely varied - leverguns, singleshot break actions, and singleshot rotating breechblock pistols (built on a revolver frame, no less)... what worked well for my Hawkeye would have no bearing on what will work well in your Contender, other than to confirm, for magnum revolver cartridges, it’s difficult to beat W296/H110, H4227, and 2400 as top contenders - backed up by the fact they remained to work so well in my Hawkeye in 256. Seems like you don’t have much to complain about with your 19.0 grn load, however!