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1/25/2018 7:38:29 AM
Posted: 9/3/2003 2:57:06 PM EST
I'm new to AR rifles, and I was wondering if this is a Pre-Ban Colt M4. Please excuse the beginner questions in my first post. Here's what I'm looking at:

Colt gray rifle, blue label box, model R6551, manufactured in early 1994. Lower is marked "Sporter Target Model Cal .223" Has the sear block.

The upper is A2, not a flat top, marked "CMB" on the handle, and has a tiny "circle in a square" as well. Rear sight wheel is marked "8/3".

Barrel is 16", has the A2 flash hider, and is profiled for a grenade launcher, has a bayo lug, marked "B MP 5.56 NATO 1/9"

Front sight has a "crown" symbol on the left side.

When I look through the vent holes in the hand guards, I can not see the gas tube due to the black metal shield inside - are these the M4 hanguards with double heat shields?

Bolt carrier has a "C"

I'm about to put a Colt collapsible stock on this rifle, so will this become an M4/A2? Or do all M4 rifles have the flat-top receiver?

If this is not an M4, then what is this called, just a "carbine"? Did Colt ship these uppers in '94, or is this a retrofit? Any explanation of the markings would be greatly appreciated.

Last question: I don't want to overpay for this rifle, so what would be it's market value in about 98% condition, with what looks like very, very few rounds shot?

Thanks for such an informative forum!
Link Posted: 9/3/2003 3:22:04 PM EST
[Last Edit: 9/3/2003 3:23:52 PM EST by shamayim]
The barrel is marked B MP 556 NATO? If so, it's not the original barrel; it's a Bushmaster barrel. A Colt barrel would be marked C MP. It does sound like the handguards are the M4 double liner type. I'm not positive, but I don't think Colt was putting that type on commercial models at that time. Sounds like a previous owners rework of the original piece. About the serial number I can tell you nothing. I have absolutely no knowlwdge of the changeover time or markings.
Link Posted: 9/3/2003 3:27:48 PM EST
[Last Edit: 9/3/2003 3:35:09 PM EST by Spooge5150]
Go to [url]http://www.biggerhammer.net/ar15/variants/[/url], and look under your model. The rifle you describe has had a Bushmaster 1/9 16" barrel put onto a Colt upper, that should have a 20" 1/7. Edit. To be a M4 you need to have. A Marked upper that has stamped 4 or M4 just above the gas tube hole as it enters the upper. 14.5" barrel 1/7 and collasping stock. M4 = Fixed Carry Handle M4A1 = Removable Carry Handle From Colt: RO977 : Flat top, Safe/Semi/Full Auto RO979 : Flat top, Safe/Semi/Burst RO777 : Fixed handle, Safe/Semi/Full Auto RO779 : Fixed handle, Safe/Semi/Burst
Link Posted: 9/3/2003 4:38:16 PM EST
I had a Colt 6551. They came from the factory in an A2 configuration with a 20" barrel, flash suppressor, full stock, and no bayonet lug. Someone has at the very minimum exchanged the Colt barrel for a Bushmaster M4 barrel and added M4 handguards. Add a telestock and you can call it an M4. [:D] As for value, I sold my complete 6551 [b]lower[/b] with Colt telestock for $1000 about 2 months ago. Figure in the price of an upper in your configuration and that will get you close to its value.
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