Ok I'm a little jealous. I'm running a BCM upper on a bushmaster lower. Although I feel that there's nothing to be gained between the bushy and colt lowers (assuming both are within spec), that little prancing pony would be purdy beside my 70 series pony or 80 series rail gun.
If you haven't bought the scope yet, give the 1.5 to 4x some thought. Even though it's not true 1x, it isn't difficult to shoot on the move with both eyes open. It's a nice option.
I have the 223 mount and it's been solid through 2k rounds. I don't like that it isn't quick release and I wish it had a little more forward mount to it, but I have zero complaints.
I test drove the leupold and Nikon options, both seemed like winners to me.
Add a bravo company sopmod stock or magpul ACS stock and it's very comfortable with that cheek weld without adding too much weight to a carbine length rifle, just my opinion of course. Plus you can store spare ear plugs, cleaning supplies, dummy rounds, batteries, skittles, one round Barney fife style or whatever you want in there.
Honestly though, if I was shooting 100-200 rounds per session, pretty much any stock would be fine.