Idaho basically said 50 is minimum for elk, moose, bear, Sheep, Goats and then they said a bullet could be no more than .010 under the bore diameter. In our case 49 is legal. My paper patched bullets are actually .496 I hunt with. I do wish that they would remove the minimum caliber and go with a minimum projectile weight. Say for elk 170 gr minimum weight.
My 45 is illegal to use for elk. But if I loaded the same bullet in a 43 Spanish cartridge it would be legal. Even though my load in my muzzleloader is much more robust than that of the old cartridge gun.
To make things worse, Idaho allows hunting elk with a 25 ACP pistol but not a 45 cal muzzleloader with a 408 gr bullet going 1400+ Fps