Nice to finally be able to buy a factory Colt carbine after such a long time. Post ban neutered unfortunately but still a great starting point for less than $1k. It has a bit to go like a sling, finalizing the light position and a LT mount for the Comp M4S but so far it is great. P-mags even drop free from it. Will wonders never cease. 
I went with the KAC MRE rail because I wanted to use the standard FSB and be able to place my X300 at 12 o’clock on the filler tube rail. I tried it but the LT mount sets the light too high. It blocks the sight picture. I set it at 3 o’clock for now. I still have to see if I’ll use the XT07 switch with or without a FUG yet. I’ll reinstall the stock SF mount as that is the lowest and works fine.
LT doesn’t make a MRE type rail but they will soon…or at least I will. Me, a LT 13.2 and a Dremel. I like their rails so much I’ll [strike]butcher[/strike] mod one soon. Stay tuned.
The Sully stock is one of my all time favorites. Solid as a rock.
The stock Aimpoint mount works well actually but that knob is large, probably for gloves which makes sense. Wonder whose mount I should use? I’ll think about it.
About the sights. The rear is the Paul Howe designed CSAT combined with a 24/7 tritium front post by XS Sights. I want to thank Justin for his incredible generosity in setting me up with these sights AND for his helpful hints for installing the CSAT. These hints allowed me to install everything in just a hair under 3 hours! F&%k this lawyering sh#t. Gunsmithing is where it’s at. 
You can see from the pics that the rear blade is horizontally grooved across its face and that the “CQB” blade has an aperture AND a squared notch. The longer distance aperture looks very much like a standard A2.
The square notch is for a 7 yd zero, the aperture for 100 yds. I shot five rounds at 7 yds, holding the front post centered in the notch and at the bottom of my target aiming circle. Adjusted to make sure my shots were going where I wanted. Then move back to 100 yds and use the peep. I used center hold on the aiming circle. Go back to 7 yds and confirm. You can now shoot from 7 to 100 yds switching between the notch and the peep at the distance you are comfortable with. Very fast and you don’t break your cheek weld. Awesome sight system. I hope I explained the sighting in procedure correctly.
Because of the CT AWB I had to use a muzzle break and it had to be pinned. I chose the PWS 556 w/the lugs for a Gemtech can like my M4-96QD. Please note that in the pics of the can attached to the upper, it is not on the lower. Why? Because in CT, the can is considered a flash hider and I would be creating an “assault rifle” if it were on the new Colt lower. So, when I want to use the can on this upper, I must attach it to a pre-ban lower. Simple isn’t it?
It’s great and MUCH cheaper to get a real Colt rather than building a rifle from parts, even nice ones. This thing ran like a sewing machine. 900 rds of M855 (one case) generously provided by some buds that I was showing the CSAT to. 