Re: Why is this so hard this year
Why not build a 220 Swift with the 8-twist? You should be able to shoot the heavier 22 bullets in it. It would sure be a coyote's worst nightmare, I would think.
But if it's a lot more range that your wanting, like say....600 yds plus, then the 6mm barrel would get the build.
Just my opinion. In your scenario though, there doesn't seem to be "wrong" answer. Just preferences.