I have read that deer can tell the difference between bullets varying 0.031" in diameter, though I am still waiting for the proof.
If you use factory ammunition, such as the Barnes Vor-Tx 130 grain bullet in a the 308 Win,
the factory claims 3125 fps at muzzle and 2,341 fps at 300 yards. If you use a 130 grain bullet in the 270 Win such as a
Winchester Ballistic Tip, muzzle velocity is 3,050 fps and at 300 yards 2427 fps. It is one of the confounding things is that 30 caliber bullets can be pushed faster than 0.277 at the same pressure. The so called "ballistic" advantage for those over the horizon shots, is mostly for those who don't shoot at long distances, and think they can hit something out there, first shot. The further the shot, the more wind moves the bullet, up, down, left, right, and in unpredictable ways. Saw the flags reacting to rolling waves of wind at CMP Talladega as the wind spills over berms. How the heck do you compensate for clockwise or counter clockwise wind when you can't see it?
I gotta tell you, 300 yards is a long way out there, not only for marksmanship, but unobstructed view. Just yesterday at the range, I was pointing to the thick underbrush bordering the range where you can't see ten feet ahead, and most of the deer hunters I know, shoot deer under 50 yards just because how heavily wooded things are.
Power line shots of 200 yards are rare, and walk out into any farmers field in the morning, and you will see hoof prints, but the deer are hiding in the underbrush in the daylight. They learn to bed down and stay hidden during hunting season. I talked to a deer hunter in Michigan who had the same experience, and he was 100% sold on his 300 Blackout AR15 rifle, he had taken a lot of deer with the thing, none more than 200 yards away. Most under 50 yards. Lots of forest surrounding fields, and the deer were hiding in the woods.
Animals have adapted to humans, such as in Elkmont Indiana. Elk there have developed types of camouflage that allows them to blend into the background, and no one notices!