Monday's Ballistics for Beginners Useful Fact :
On a traditional rifle with a curved stock, a 3" high scope makes you lift your cheek off the stock and the scope recoils into your eyeball. So high sights are evil, OK?
No! High sights are good! Mostly!
The dotted line (1" high sights) is further from the gray target area than the solid (3" high sights) line. So the low sights move the trajectory more off target. Same ammo, same zero. At 10 yards 3" sights are worse, but maybe you don't have to aim too carefully at 10 yards anyway. The high sight is better from 50-300 yards. Just what you want for shooting at things that roam about the place.
But the AR-15 has a straight stock, it is designed to have the bore 3" below eye level.
There is no advantage in mounting the sights lower with the straight-stocked M16 family.
You see people with low sights on flattop AR-15s with the butt half off their shoulder to raise the sights to eye level. This is awkward, and places the bullet further off target at the high point of the trajectory.
When the SA80 rifle was introduced with higher sights than its predecessor, British armouries were soon sporting a poster with a soldier looking over a wall through the optical sight with the muzzle touching the wall. The caption read something like "don't do this". So don't do that. Walls are expensive. But otherwise high sights help you hit the target, as long as you have a comfortable cheek weld on the stock.