Those rifles were intended to be issued with 2.5-8x Leupold MR/T scopes. Each branch of service used their own version of the optic, but they're all the same short of knobs and either mildot or TMR.
I built a "recce" rifle which a 16" navy improved version, they were allowed more leeway in stocks and hardware but it's basically the same rifle with a different barrel. Some use the same scope. Others use the NF 2.5-10, which is nice, but honestly for what a 5.56 can do the MR/T is pretty nice for the price. Your idea of the B10 is exactly what I'm doing with my 20" Grendel. But my 16" sports the MR/T because I happened to have one I got for a good deal from a member on here. It's a fine scope for that rifle and for that price. A NF 2.5-10 would be nice too, nicer in fact, but I do like USO and the B10 is a fine looking scope. I have a 1-8x, 3.2-17x and 5-25x. They're all excellent optics, first class. They're also tanks. The B10 is smaller but it's still hefty. The mil/mil version with the GAP reticle is one of the lower cost versions and I have that reticle in the LR17 and ER25 and it's a great, simple reticle to use. The 1-8x has a blue tree, not my favorite color but worth it for this fine optic, and I really don't use the tree, but those 1-8x optics work like illuminated reflex sights at very low power, and like FFP scopes at ~3x or so and above. Discontinued, but an amazing AR optic if you can find one.
I'm not a big fan of lots of mag on a 5.56 so I think you'd be better off with the 2.5-10, 1.8-10, 2.5-8x or even a 6x ACOG or 1.5/6x Elcan. Or a VCOG. There are lots of good choices, all better than the Mk6 IMO.
If you want that kind of mag, I'd consider the 4-16 ATACR. FFP and you can get it illuminated and with practically any reticle. Look for sales, and fancy reticles cost more and aren't necessary IMO for a 5.56 AR but I consider illumination these days to be standard on a high end scope.
That Mk6 is for non-illuminated I bet. For some reason Leupold charges a helluva premium for reticles and illumination on their Mk6 and Mk8 scopes. Nevertheless, people are saying stay away from Mk6. Also, look at the sticky on the optics forum for a tracking test a member did. VERY informative! And he evaluated for more than tracking. You would do well to look at that before making a decision, even if some of the scopes tested aren't the same model you'd buy. Good luck. And as long as you get a quality scope and it has what you feel you need, you'll likely be satisfied. Remember people tend to get more mag than they need, so try to keep that down if you can, but that's totally up to you too. And read that sticky.
Just my $.02.