I'm with statdoc, again. The main question is whether you want magnification. To be honest with you, the AR you are working with is not something that is meant to have a big magnification scope so the amount of magnification you'd be looking at is something like an Aimpoint 3x along with an Aimpoint sight. I think that with an AR 6940 you'd want something for quick target acquisition so something like an EOTech would be great. I have an EOTech 512 (AA batteries) and it is quite nice. The can be had for a pretty reasonable price too.

Isn't is crazy what you can spend on optics?

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