It depends on where in Oreagon you are hunting and if you are skinning and selling the hides..
20cal is good, and pelt friendly, cheaper to reload and flat shooting. Its more effected on wind drift than bigger bullets, but it's easily manageable.
If you are out in the central and eastern parts of your state, where shots are longer, i might suggest something a little bigger.
If you are not skinning at all, go 6.5
In eather case I like Vortex scopes with something in the 4-12 or more range, less than three isn't really needed. I like to carry a shotgun on stand for anything inside 50yrds anyways.
Personal choice if i was out in central or eastern OR, and reloaded, I would do the 6x45 with a 4-12 bullet drop type of reticle, and a 12g shotgun that takes 3" shells.
If i was hunting coastal or NW parts, and didn't reload 5.56 and run some 53gr 223 ammo with a 1:9 twist 18" barrel.
Good luck making a choice.. There is just so many to choose from it's almost to tough to just get one. (hint)