I have a FastFire II mounted to a Glock 20SF (10mm). I love it, works great. If it can handle the recoil mounted to a slide, I’m sure I’d be fine on an AR. I did some comparisons a couple years back when I bought it & I just couldn’t justify the cost of the others. If I had to do it over again, I’d get the FF III. I’m sure others will suggest getting the RMR or Delta Point, which are great optics but it’s also a lot more coin to drop. You’ll have to decide if the extra $'s is worth it. For me it wasn’t.