What exactly do you want to do with this rifle? Will you be competing with it in a class that requires irons?
Your particular AR15 was specifically intended to be used with a magnified optic, not iron sights. The PRI flip-up would be one to consider:
http://www.mountsplus.com/mm5/graphics/00000001/PRI-FUP-001.gif
You could still use optics with it folded down, then flip it up and use your rear sight in conjunction with it for whatever it is you intend to do. From my perspective as an avid and long-time AR15 owner, it looks like you're wanting to take the Digital Electronic Engine Control off of a nice sports car, and replace it with a 1910-era distributor, but it's your gun and you are totally free to equip it with whatever aiming system suits your needs.
A 24" barrel AR15 usually does duty as a varmint slayer, or intermediate to long-range recreational target gun. With certain projectiles, it is easily capable of making predictable hits at 1000yds, especially if you single-load the VLD-type pills, however, the CR6724 has a 1/9 twist last I checked, which will limit you to the 69gr SMK, but you can run it very fast for the 600yd line.
If shooting varmints, you will be using good optics and high magnification usually. Target shooting can be done with both irons and optics. Most AR15's set-up for iron sight matches are configured as service rifles in appearance, while race gun AR15's are equipped with the sleeved target sights that clamp on to your barrel as ORD posted above in post #4 of this thread.