I have three AR's, 2 of them have an EoTech 512 and the third one has an EoTech 552. If you are talking about a scope, I can't help you with that. All of my hunting rifles have cheap scopes. All have a Tasco World Class 3X9X40 except for my 270, it has a Bushnell Banner 9X18X60.
If you get an EoTech 552 be careful and only buy from a reputable dealer. There are several counterfiet/fake 552's on the market.
on my 270 I have a Leupold Vari-XIII 3.5x10x50... I bought this scope 17 years ago and have been very happy ever since. You can still purchase this same scope, and its a LOT less now...
My suggestion would be a Zeiss Conquest scope. Better glass than a Leupold and in the same price point. I have a Zeiss Conquest 3-9X40 RapidZ 600 retical topped off on my Springfield M1A Supermatch. Once I worked up the best load for my rifle and got the balistic data. I went to Zeiss's website and entered the info in their ballistic caculator and it gave me the point of impact from 100 to 600 yards with my load.