I saw a couple flip up rear sights with a Same Plane Aperture feature? It got me curious and I read what i could find about the idea. So what am I missing? Why aren't all rear AR style sights using this design?

Can someone explain the choices between the same plane and A2 standards?

thanks,
mike

So I guess until I read about this I would have assumed all sights were like this... why is the A2 not a same plane design? happenstance? Or is there some reason?

thanks,
mike

The military thinking on the sights was that you'd use the small aperture for precision fire from 800 down to 300m by dialing the wheel and then the switch to the larger "0-200m" aperture included a switch to a 200m zero.  Probably was a bit of a carry-over from the A1 sights where the apertures were the same size but with different offsets so that you changed ranges by flipping back and forth.