It can't be beat as an iron sight, however, you pay for it. - Ultradyne C4 Flip-Up .223/5.56 Dynamount Front Sight

I've never used a more intuitive, accurate iron sight, but, although the sight will mount directly to most threaded AR15 caliber barrels, you will need to purchase a brake/compensator, muzzle break, or flash-hider from Ultradyne in that caliber to mount the front sight. However, you could get away with one or two rear sights. These are quality sights, with an excellent finish, and quality hardware and material. Before buying, look up the Ultradyne website, so there are no surprises, plus you can see the different options and compensators available.