I have a preban Colt Sporter Match HBAR, serial# MH004***. The entire rifle is in excellent condition, very few marks and a couple of scratches on the A2 buttstock. It is a large-hole lower, with Fwd Assist, but no raised mag fence, with a small-hole Colt A2 upper. Upper is 20", has flash hider, no bayo lug, and the barrel is marked "C MP 556 NATO 1/7 HBAR".

Any information on this gun? Price? Thanks for your help!

I'm thinking the gun you describe is a Blue Label Model #6601 since no bayonet lug but with a flash-suppressor.
You don't say if there's a box nor do you mention any other accessories so I'm thinking in the $1200 - $1300 range.  (I'm also assuming this is a pre-ban rifle.)

$1000-1400 depending on your market. Assessories, mags, and the factory box all add to the price. I bought a MH 6601 in Oct and paid $1000.  I was hoping this was an indication prices were on the way down but it just looks like I got a good deal.  However, I'm puzzeled that your lower is a large hole and your upper is a small hole. I have seen blue lables with both large & small hole lowers but the uppers have all matched. Is it possible that the upper is not original to the lower?  

Quoted: Is it possible that the upper is not original to the lower?

But his barrel with the 1:7 twist is correct for this model.

(Nice buy for $1,000 !!)

You guys are both right.  It is an R6601 lower and it is preban.  The S/N cutoff is MH086xxx.  I have seen a lot of 6601 rifles, but never one with different hole sizes in the upper and lower.  I wonder if someone custom built the upper and as 5sub points out, used the correct barrel?  However, you never know with Colt.

Quoted: However, you never know with Colt.

So true.

Thanks for the input thus far guys...I bought the rifle the other day. It came with 1 20rd Colt mag, but that is it. I really had my heart set on a 16" carbine, but this preban deal came along and the price was so good that I had to take it. Do you guys think I could find someone willing to trade a 16" carbine preban config upper for mine? Thanks!

Duck, you might find someone who is willing to take a partial trade.  However, the carbine uppers are in far more demand than the HBAR's so you will likely have to generate some cash as well.  Watch the equipment exchange for trade and sale opportunities.  Many times buyers will accept a trade if you offer one, even though a post is looking for cash.  If you want to purchase something like a quality M4 upper, check with someone like BarSundown.  I have seen his stuff and it is always of fine quality.  Be aware that true M4 uppers run in the $500 - $700 range, depending upon use and quality.

If you just want the 16" barrel and dont mind using your current upper receiver just buy a barrel assembly and have a gunsmith install it.
Thanks what I did with mine.  Bought a BM 16" M4 preban barrel from a wholesaler in SGN for $189 and my local gunsmith swapped barrels for
$25.  You use your current B&C and CH.  Saves you about $100-150.  

If I buy a pre-ban 16" barrel, I will need to buy CAR handguards right? I don't mind using my current upper..I just want 16", flash hider, and much lighter weight. I assume that by replacing the Heavy Barrel with a carbine one, the overall weight (as well as length) will be greatly reduced. More input? You guys are awesome =]

duckfsu, most manufacturers (Olympic Arms is the only exception) will include handguards with the barrel assembly.  The shorter barrel will reduce weight by maybe a pound.  If you really want to go lighter you need an M4 profile barrel or LW barrel.  Now, if you are only looking for less weight, you may want to consider haveing your Hbar reprofiled by Kurt Walla at Kurts Kustom Firearms.  He will do an A2 profile that will cut about 1 lb for $55 + shipping and he will remove and reinstall the barrel.  He can also do A1 profiles and other custom barrel mods.  He has a forum here in the Industry Forums.  Money is the only factor in what you want to do with your AR.  

Well, my inattentiveness to detail led to me being wrong again. I just took the upper completely off, and it turns out that it is a large-hole upper as well. There was no adapter-bushing-thing, just the screw. Does this increase the value of the gun at all, since the lower and upper are both large-hole and matched? Thanks!

Quoted: Well, my inattentiveness to detail led to me being wrong again. I just took the upper completely off, and it turns out that it is a large-hole upper as well. There was no adapter-bushing-thing, just the screw. Does this increase the value of the gun at all, since the lower and upper are both large-hole and matched? Thanks!

In my opinion no although the previously described set-up would likely have decreased the value.

If the barrel length is alright you might just have Kurt flute your barrel - you'll lose some weight plus add a certain amount of "cool" factor.
(Not that any of us hard shootin AR guys care anything at all about cool !  I do have an ArmaLite M15A4 with a vertical pistol grip, laser and tac light hanging off the rifle but that's only because I 'NEED' all that stuff.)

Think about your likely shooting distance and over-all expected use before going to the carbine as you're going to give up some velocity.

Well, I figured out what I'm going to do...feedback is appreciated:

I'm sending my upper to Pete-in-NH of Legal Transfers tomorrow. He is going to re-barrel it with a mint like-new preban 16" Colt Lightweight 1/7 twist barrel with A2 hider, bayo lug, and M4 handguards. I am also getting a new black RRA 6-position collapsible stock from Pete. All together, it's going to cost me $452, which includes a gas tube, labor, and all the stuff above, as well as return shipping to me. This way, I'll have my original barrel and handguards that I can either sell or keep to be able to restore the gun to original condition. I paid $900 for the gun, and with the $452, this gives me a preban Colt carbine for $1350, not subtracting what I could get for selling the 20" barrel and handguards..that is good, right?

What do you guys think? Good deal? Good idea? Thanks! :)