Re: Magpul MBUS back up sights.
What I have been using lately is the Diamond sight.
I was told that it "just works" when I asked about them.
When I looked through them it did, simple as that.
My eye aligned the diamond aperture a hell of a lot faster and more precisely than the other manufacturer's sights that I have used for a few years now.
Good quality, locking, very low profile sights.
No external springs, very sleek and compact.
These are the original Diamond Sights that were invented by Dan Ballard. Briefly these sights were produced at Troy until Mr. Ballard decided to make his own sights.
I haven't used the ranging front sight yet but it makes perfect sense.
If the front post on the ranging sight (one of six, 100y-600y) matches the man size target then that is your range. Dial it and shoot.
All of the sights locking, non locking, ranging (.223 SS109) and the vertical grips are attached incredibly fast and strong with D-Loc rail mounting systems.
I will have a much more in depth review on the Diamond Sight BUIS very soon.
Hope this .02 helps.