If you are thinking in line of a Tactical type optic and not a scope.
The ACOG sight is a fine sight but also has some factors to consider. That being it has magnification so it makes any cowitness with the iron sights impossible. One must plan on using it exclusively. My recommendation would be a Aimpoint Pro or one of the EOTech Models with the 123 battery. Both have cowitness capabilities. If price is an issue you can go with an EOTech Model 512 or similar optic which uses AA Batteries. For them I would recommend Lithium AA Batteries or Industrial grade AAs.
The Constitution is not an instrument for the Government to restrain the people. It is an instrument for the people to restrain the Government!
Today, we need a nation of Minutemen, citizens who are not only prepared to take arms, but citizens who regard the preservation of freedom as the basic purpose of their daily life and who are willing to consciously work and sacrifice for that freedom."
Magnification notwithstanding, IMHO, ACOG is the way to go. 3 to 4 power is perfect. Good for CQB and out to 500 yards.
And I looked, and behold a pale horse: and his name that sat on him was Death, and Hell followed with him. And power was given unto them over the fourth part of the earth, to kill with sword, and with hunger, and with death, and with the beasts of the earth.
Using a Kahles K16i 1-6 and could not be happier. Was using the NF 1-4 and its a great scope but I wanted a little more mag. It's pricy but sometimes ya have to get a little crazy .
The thing I like most about the scope is the lack of tunneling and distortion at 1X and with a ridiculously bright reticle, it takes the place of my EO tech so, I can use it on the shorty and it works well on a 20" as well.
depends on what your goal for the rifle is. my ohsht gotowar carbine has an acog and its pretty much strictly a gun that is sitting in the safe for when folks figure out how much hell obamacare is going to give em and the looting and rioting start.
it also has buis but anything that is capable of breaking an acog is highly likely to kill you and put the rifle out of commission anyway...
"Gun control: The theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound." — L. Neil Smith
The problem with being stupid is you cannot simply decide to stop doing dumb things...
"I crapped my pants to avoid the draft!!" -Ted Nugent