a long way
As has been noted now by several posters, 400-600 yds is quite a poke. I don't know about the OP's "friend", but I wouldn't be confident shooting at any big game animal at such distances.
Rangefinders and optics have changed the game, but what hasn't change is the wind, shooters ability (or lack of it) from field positions, and animal behavior. Shooters without a laser will need to be good at range estimations. Long distance hunting is all the rage these days, but most game is likely killed under 300 yds,and with whitetails, I'd wager under 100.
For anybody considering such long shots, I'd suggest the following. Take a standard white paper plate 9-10" in diameter and staple it to a tomato stake. That is the vitals of your "trophy deer". Find a place you can safely shoot 5-600yds.......and that won't be easy for a lot of us. With your rifle, from field set ups, (say over a pack) without ranging shots or sighters, in a reasonable time frame to simulate hunting conditions, take a shot. I'd bet over 75% of folks trying that will miss, especially if it is not a known distance. A miss laterally due to poor wind read, is a possible gut shot, and a low shot, due to error in ranging, is a possible broken leg. Heck, a lot of folks will miss that shot at half the distance.