It's all been said, yet..
While a friend was setting the scope on one rifle, I hit the 300yd 4"x6" metal plate on a piano wire on the first shot with just the stock iron sights. He looked at me stunned, yet really, a good rifle should be able to do this if you just relax and pull the trigger the split second you know you're on target.
Awhile later I did a one-day training with the trainers of BlackWater. We were under live fire all day, rifle to pistol, jammed loads, clearing, reloading, fire fire fire, bullets over our heads and next to us, etc, shooting at 8" metal pie plates set up 4' apart x 8 of them, at 20-100yds, plus some standard body forms. We probably shot 10 30-shot mags each. (I agree the 8" start to look huge.)
I was using a borrowed rifle from the squad, a cheap old thing, with a $100 Tasco red dot, no tweaking, no resetting, just "here you go" and off I went.
I knew I was hitting everything I was aiming at, yet couldn't really hear it with all the others wailing away, nor see any sparks very often. End of the day I have a full mag, its dark dusk, they want to quit, and I want to shoot. Finally a woman trainer says she will spot me, and at 70 yards or so I cranked off 28, 29, 30 out of 30 at the pie plates pretty rapid fire changing right to left to right in random order, and that little red dot seemed to glow every time the target was seen. Instant pop, sparks flying.
I learned that day that its truly 'see it and shoot the split second you see it', and that most of the misses come from thinking, waiting, hoping, wishing, and pretending I can't see it, or whatever.
So...100yd, naked eye, or red dot is PLENTY. Add out to 400yds onward, get a scope.
