by SayItIf you are are stable in crouch or prone on the ground. And you cannot make a vital shot with irons on an AR at 300 you suck. I can do that shit on my uncles shitty wasr 10/63. The OLD one without the tapco trigger upgrade.
I'm talking about a military sniper. They would never allow a sniper in the military to take out a sensitive target with iron sights even at 300 yards. Sure you can hit your target but the chances for error are considerable increased. Compared to a scoped M40 that you could drop one in his eyeball at 300 yards with very little effort. It's just common sense.