I have a friend who is interested in building a super accurate rifle for deer hunting out to 500 or so yards. He is not a handloader, nor is he likely to be. I can get the rifle built, but I am trying to figure out a caliber to suggest. He will be hunting whitetail deer over agricultural fields. The parameters are good available factory ammunition and a flat enough trajectory to minimize holdover with about a 200 or 250 yd zero. He also doesn't want excessive recoil or a muzzle brake. I think he would stay away from a .300 magnum, but a smaller magnum would work. He is currently shooting a .30-06 so it has to be something flatter than that. I have a few thoughts on calibers to suggest, but I would like to hear from you guys.