DARK...
I've forgotten more than most ever knew, as I have many other things to shoot...
I used "pressure" as an easy to use term... more proper would be breech thrust, or one of another scientific terms... for pressure 4exerted against the mechanism ( it has as more to do with case head diameter, & pressure, in some kind of formula, that just chamber pressure )
since you have the pressures handy, or cared enough to look them up... TC did make Contender barrels for 375 Winchester, but "rumor" has it, that's the max that TC feels the gun can handle safely with repeated use, they do not make barrels in 444 Marlin, but some after market companies do, so that one is just over what TC feels the gun can handle, & the 375 is the maximum ( pressure / breech thrust... whatever ) they do not make barrels in 220 swift, 22-250, .308, 30-06, or any of the magnum cartridges ( that I know of )
that is what the Encore is for ( the Contenders bigger brother ) ... in fact you can get Encore barrels in the likes of 416 Rigby, 300 Win Mag etc...