I have a Hawke 8:32x56 on my AR20 and love it.
No problems with it and it's never let me down.
Range finding is spot on.
Only thing is you will need a bigger wheel, the markings on the wheel that comes with it get cramped together after 45 yards as it's too small.
There is a 6" wheel available for £30. should you buy the hawke and it works perfect.
Hope this helps.