Thanks guys. I used a 300 Norma Mag that I built. Arrowhead Obsidian Action (by Kelbly). Bartlein Barrel. McMillan A3 Stock. TriggerTech 2-stage, Kahles K525i optic. And a prototype bipod from Rokstedi that should be on market any day now. 600 yards is a poke, but not nearly as hard as it used to be. With a good rest, the only challenging part is making a good trigger squeeze and a good wind call. I ended up a little back on the shot, but shooting a big mag like that does give you some margin for error and it all worked out.
All my buddies down here were telling me it could be a decade or more before I went over 120" again after doing it on my first Coues hunt last year. Couldn't believe it when we located this guy first evening out and then sealed the deal next AM.
They look like little Iowa whitetails, but have totally different personalities.