I totally agree with you 100% on the .303 and the rest of the rifle rounds you mentioned here~ 😎 👌The .303 would be a good choice for the rifle in the game, considering history, location, as well as muzzle energy and velocities. No argument there whatsoever. I'm just simply asking why the rifle has a specification for caliber and not the revolver.
See now, IMO, you're forgetting where you are at in this game. Out in the wilderness, sparsely populated with a majority of the game being medium to large size aside from the wolves and rabbits. As a revolver for a backup, do you reeeeeally want a .38 spl to ward off a wolf or worse, a bear or moose? 🤣 No offense to .38 spl fans or the caliber itself, but as a backup in the wilderness, it is extremely underpowered, even if it was a +P cartridge (which is pretty much a compromise between a normal .38 and the .357 Magnum). You would really be better off with something that has at least if not close to 50% of the velocity and energy of the .303 or whatever hunting rifle you have, and either a .41 Magnum, .44 Magnum (.429 actually, but who's counting, right?) or a .454 Casull (which is a lengthened and strengthened .45 Long Colt) will certainly have that, especially if you have a hot round like Grizzly, Buffalo Bore or Underwood in the cylinder where you're easily throwing bullets out with at least four-digit energy and velocity. Even a really hot .357 Magnum would be a good start.
Anyways, not trying to start a fight or anything~ I'm just stating what I think would be best based on the numbers for all the possible calibers, their availability, the location, and the history of that caliber, etc. Just my two cents~ As a backup, I would happily take out my Ruger New Model Blackhawk in .41 Magnum with some good 265-grain Underwoods~ Cheers, all! 🖖