Huh, I was trying to quote and it posted straight away. Anyway.
I just went through all of this outfitting my Remington r-15. The Armalite is nice but a tad low. The Larue's are the cats meow but pricey. You also have to look at the eye relief of the scope you end up with and what stock you have. I mounted a DMS to mine with the fixed stock and A.R.M.S. 22H QD rings directly to the rail as far forward as it would go and it sits perfect. I can not get any closer to the charging handle because of the stock. If it was a colapsable stock, then I would need it further forward.
I see someone posted the link to all the one piece mounts. That is an awesom thread. At the bottom is another option. GG&G makes two scout rails. One allows room for a BUIS at the back of the stock rail, the other covers all the way to the rear. If you mount this, you can use any low QD rings and have enough options to get the correct height and eye relief. Since you are using the .50 hight rail, you will most likely end up with low or Med rings and could then swap the optics to another bolt action and not be too high.
I just purchased a SIII 6-24x50LRMD. awesome sope. Great glass, great feel to the turrets. I would definately look at this scope. 100moa as well and good eye relief. I was looking at this and the elite 6500 and chose this. The 4200 is a great scope. the only downside is the 45moa but if you don't plan on shooting past 600 or so you would be fine. And even if you did, EGW make a 20 moa base like the GG&G for the AR. The you just throw the scope in some QD rings.
Hope this helps