I've been using the primary arms 1-4 with their exrended mount for over a year now in multiple 3 gun matches. I'm very impressed with it. Its never lost its zero after being thrown around and banged up against barriers.
For around $150 with mount, it just cant be beat.
They also have a 1-6 out now for about $250 if you want more magnification.
I just got one for my wifes 3 gun ar and sighted it in yesterday. seem to be decent glass. the only thing i dont like is the big turrent knobs. i can see the possably getting hit when dumping in a barrel. time will only tell