I am in love with the acog. I have a 3x for an AR10, and two 4x for .223s. They are clear and super durable. There is nothing better, especially when in a larue mount. And that from a guy with 5K invested in them. I can hit a 24 in. manhole cover at 600 yards every shot with any of my acogs. Not bad for a 3x optic.
I recommend this one:
http://www.laruetactical.com/trijico...ue-lt100-mount