If I was to shoot coues deer over 500 yards, out to 600 (been there done that, multiple times) then I would shoot my .257 wby.
But, when you get past 600 yards, I would actually change to at a minimum 270 wsm, but I would lean more towards a 7 rem mag, or even better yet a 7 RUM with 160 Accubonds. I have been threatening for the past year or so to send my dads Leupold from his 7RUM to get the turret treatment, load up some 160 Accubonds and get to the 800 yard range.
