Anyone have a photo of a setup like this? Can be an A1, C7 or A2 upper.

http://www.thenewrifleman.com/ (ARFCOM user name Knife_Sniper)

^ Pretty much that sums it up - I don't have pics but my issued weapon on deployment right now is an A2 with a KAC rail with a M68 and PEQ15 on it. Kind of silly looking, but the red dot still works on it fine.

Here's a picture of an A2 with KAC M5 which belongs to member Bayer.  He posted this pic in the tacked A2 picture thread.  Thought I re-post it here on this thread (hope he doesn't mind)

Thanks. Stickman had one a while ago with an A1 upper and 7" Daniel Defense Lite but I think the pics have been deleted.

I'm building a simple short barrel upper with fixed sights and an Aimpoint in between them. I was planning on going with a flat top upper and a DD A1.5 rear sight but am thinking about using a C7 or A2 upper. Any thoughts?

M2 or M4 Aimpoint?

My recommendation is to stay with an A3 upper (flat-top), use a free-float handguard, detachable rail-mounted sights, and use an Aimpoint T1, M2, or PRO for the optic. The T1 keeps everything looking clean and lightweight. The M2 and the PRO will give you a broader field of vision. Using a C7 or A2 upper will result in the optic having to be mounted high or forward of the carrying handle. The A3 upper is much easier and more versatile to work with. For a front sight, you could use the Daniel Defense Fixed Front Sight which would compliment the Daniel Defense A1.5 Fixed Rear Sight.  

I miss this old girl....

Anything you didn't like about it?

That's what I'm thinking.

http://www.whiteoakarmament.com/xcart/product.php?productid=17551&cat=259&page=1

Brownells sells Rock Rivers NM float tube, and WOA sells theirs too. From my understanding any A2 handguard will fit on them with a little work

I put an M5 RAS on my Colt 6551 a few years back and I'll never do it again.

It was heavy as hell and the RAS didn't really bring enough to the table to offset the weight penalty.

I traded a problematic RRA for a new 20" FN 15 a few weeks ago. I'm thinking about putting a new chf barrel on there and a free float rail. Do you guys have a recommendations to make this as solid as possible? Any parts I might need to do this beyond the obvious? Possible conflicts in hardware? The is my first barrel related mod.

Why change out the barrel? Also, I cannot understand the need to go with a FF handguard unless you are looking to shave some weight off. Firstly, there is nothing wrong with FNs barrels. They are some of the best you can get. If you are wanting to put on a FF handguard, just change out the FSB for a low profile gas block. Also, depending of the FF handguard, you may have to remove the Delta ring and existing barrel nut. Many of the newer FF handguards come with a proprietary barrel nut. I would not change the barrel, that is unless you just want a stripped barrel to use and you intend on selling the FN barrel assembly intact. Secondly, why not just buy a new upper receiver and build off of it and sell the complete FN upper assembly or save it for another build?

The KAC M5 RAS is not designed to save weight. It is made to be a versatile drop-in handguard. It does have its place and serves its purpose very well. I love having it on my A4 build. If you want to save weight and have a versatile handguard, you need to go for a free-float handguard. That would entail a few modifications for it to work with a Colt 6551 HBAR. First off, the main source of the weight is not from the handguard. It is from the barrel. It is going to be heavy regardless of which handguard you use. The KAC M5 RAS is not much different in weight than the A2 handguards. Even changing to a FF handguard, you may save a half pound (8 oz.) or so. That is negligible. If you really want to lighten up the Colt, buy a standard A2 Gov't profile barreled upper and just save the Colt HBAR assembly. HBAR rifles are that weigh for a reason. The weight improves the accuracy. These are generally match rifles, not general purpose rifles.

I second keeping the barrel. You will not likely realize the differences of a CHF barrel vs the stock FN button rifles barrel. Don't get caught up in the CHF hype.

Evaluate the barrels accuracy with quality ammunition after you free float it and then decide if you need a new barrel. In a semiautomatic you are not likely to push that gun to an level where you would notice a benefit to CHF in the due course of the rifles operational life.

As far as the FF rail: I recommend a traditional tube type FF rail as they seem to be exceptionally strong. Something like the now old Larue 12.0 or the armalight  quad rail. These rails employ a steel barrel nut and while they may appear outdated... They are extremely strong.

A AMU shooter reveiled to me in a personal IM exchange that he did not recomend the DD style free float rails with the "bolt up" system due to the bolts shearing from sling torque. He and several other shooters replaced the DD units with the old armalight quad rail.

So while thats not a personal experience, it was enough to keep me away from the DD rail on a 20 inch build. If you think about it the sling swivel mounted all the way at the end of the rail would put a tremendous amount of leverage on the mounting system and hence sheared bolts on DD rails.

The traditional tube quad rails place all the stress of torque on the receiver since the quad rail and barrel nut are tightly mated to each other.

Tube systems such as the Larue, armalight, and the new giessele quad rail would be your best bet for free floating a 20.

FWIW, the 6551 is a govt profile, not HBAR. I'm not planning on running a 203, NV, or IR devices on it, so the RAS was essentially a big light mount. It was a quick experiment and I came to the conclusion there were better ways for me to mount a light on an A2. YMMV.