Zak has written a very interesting article on “Fighting Optics for the AR-15”. He focuses on M4 type rifles and SBRs (Short barreled rifles).

Now that optics have come of age on fighting rifles, one of the most compelling reasons to have a longer barrel has been removed. With iron sights such as those on the M16A2, practical accuracy depends on sight radius; it is easier to shoot accurately with more distance between the front and rear sight. Optical sights have no sight radius; barrel or weapon length is now separated from the ability to obtain a precise sight picture. This change allows a 14.5-inch M4 to have the same sighting precision as a 20-inch M16A2 or even sniper rifle.

M4 with Trijicon ACOG 4x

Read it here.