AR15 Rifle -vs- M4 Carbine??

[Pete D.]

hmm.

That's a pretty big if. I don't know anyone who is talking about accuracy in a 16" or 20" barrel for 400-500 yards that isn't using a scope.

Then you haven't been to a High Power Service rifle match. Accuracy is the name of the game. Only iron sights allowed. Slow fire is at 600 yards.
Also, you don't know me outside of these posts of course but accuracy is important to me and I shoot only iron sights.
This guy is in the offhand stage at 200 yards:

 

[Welding Rod]

Fine accuracy, using iron sights, matters a lot in High Power. In my club the best shooters will be seperated by a few points out of 500 possible. It is not uncommon for tied scores to come down to X count, Is is not uncommon for tied X counts to come down to man on man shoot offs.

The ARs on the line are all 20 inch. That is what I shoot. I have a 16" LW barreled AR too that I shoot for fun, but I wouldn't select it for a match. No sense in giving up sight radius when you are shooting to win.