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Posted: 4/1/2026 10:58:46 AM EDT
[Last Edit: Roycephus][Edited]
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I’m trying to figure out this site. Not many directions. I have a Colt AR15A2 Gov’t Model. Serial GS 0088XX. I bought it about 7 years ago for 1k and have completely forgotten about it. Upper receiver marked CM. Barrel normally marked C MP 5.56. Neutered BCG, but with proper C, bolt MPC. The problem I’m having is the FSB is marked 2BI1, (2 BRAVO INDIA 1) I can’t find any info on this, the FSB is marked with an F also, which intuitively tells me it’s wrong. Help. This is 20” A2, not the Gov’t carbine. |
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Pics would help. The proverbial "F" on a flat top upper compatible front sight base will be engraved/cut and not a forge code proud of the surface. Otherwise those forge codes are just tool/batch marks and don't really provide any relevant information that I've ever seen anyone identify. ETA: Yes, Arf is vast and "wonderous" LOL... There's some tacked threads at the top of the page in this forum and the A2 Builds forum with good info on model variations and details of small parts as the rifles evolved you might peruse. There also used to be some great non-forum guides, but the links to them keep getting harder and harder to find. 
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Try here Note sure how much help you'll get from any mods on navigating the site. |
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| I have a 92xx GS and the sight base is blank of any forge or other type markings on it. Nothing but the UP at the sight post. It is a shaved bayo lug one unlike some of the earlier ones that still had the lug. Honestly, I would have swapped the barrel on it if I had ever run across a good Colt barrel with the lug. Had same stupid shaved carrier that I did swap to a like new sp1 style Colt carrier. |
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Originally Posted By Roycephus: I know Colt markings can be hit or miss, but why would I have an F marked FSB on this. From what I understand these are pretty rare. Not at all, F height front sight bases became the mil standard after the M4 was introduced and Colt eventually used them across the board, even on the 20" rifles. I would guess either a new barrel was installed as j3_ suggested or it's not an actual F height front sight base and you're just confusing the gobbledygook forge codes. This is why a photo would help us help you identify what you have. Does the front sight base have a bayonet lug? |
| Good info on small parts and serial numbers here: https://www.biggerhammer.net/ar15/ |
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| I haven’t touched this thing in 7 years, cleaned and oiled it and it’s been a relic ever since. I have the hand guard off it now. Can’t find a date. Again, barrel is marked C MP 556 nato. This is supposed to be one of the rarest Colt AR15A2 models, maybe I just got a lower/upper combo and barrel change with FSB change also, why would an A2 upper receiver have an F marked FSB? 2BI1….2 bravo India 1? |
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Originally Posted By Roycephus: Colt website for serial number lookup results in nada. The GS SN prefix is goofy, I spent years trying to figure mine out and back then, info was stupidly hard to come by. It's better now but not by a whole lot. Mine has the shaved carrier [well had, it has a standard M16 one now and the original is in the parts box] and cut bayo mount but that is it, it doesn't have the receiver block in it. Mine came with the rubberized scope, Colt mount, Colt cheekpiece and the Colt .22 conversion unit. To add, mine also came with the M16 [nylon field type] cleaning kit and the 5 round mag. |
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I'm getting down to the last box, the others have all been destroyed...
I'm getting down to the last box, the others have all been destroyed...
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Originally Posted By Roycephus: This is supposed to be the holy grail of AR15A2/M16 Colt put out. I can’t post pics. I gave all the information in the beginning post with my questions. No, it's really not, it's just a regular AR15 put out at the time but with a GS prefix that seems to be somewhat of a short run. I will say mine is stupidly accurate but Colt was putting out very good barrels at the time. |
Liberals are a curious mix of communism and fascism, they want to destroy you but want to use your own money to do it.
I'm getting down to the last box, the others have all been destroyed...
I'm getting down to the last box, the others have all been destroyed...
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| https://ar15.com/forums/ar-15/Colt-R6550-Gov-t-Model-AR15A2-GS-prefix-Research-Project/127-782309/ |
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Over 50 and reputed to be a formidable brigand
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Over 50 and reputed to be a formidable brigand
https://hr1871.com/
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Originally Posted By mike_nds: https://ar15.com/forums/ar-15/Colt-R6550-Gov-t-Model-AR15A2-GS-prefix-Research-Project/127-782309/ Yeah, mine is in there with the ammo cans in the background. |
Liberals are a curious mix of communism and fascism, they want to destroy you but want to use your own money to do it.
I'm getting down to the last box, the others have all been destroyed...
I'm getting down to the last box, the others have all been destroyed...
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The 6550 is the closest A2 spec AR15 Colt ever made. GS is Colt speak for “Government Sevice”. I owned 000460 for twenty years years before selling (regurts) it. My recollection is it shouldn’t have a F marked FSB as it isn’t spec for an A2, mine did not. Yours is a late serial number production and the M4 barrel was being produced early as 1989, but that doesn’t mean someone on the factory floor didn’t “make do” to finish a build to get it out the door. |
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Originally Posted By 11b4v: The 6550 is the closest A2 spec AR15 Colt ever made. GS is Colt speak for “Government Sevice”. I owned 000460 for twenty years years before selling (regurts) it. My recollection is it shouldn’t have a F marked FSB as it isn’t spec for an A2, mine did not. Yours is a late serial number production and the M4 barrel was being produced early as 1989, but that doesn’t mean someone on the factory floor didn’t “make do” to finish a build to get it out the door. Actually, that would be some of the law enforcement only products Colt made during the ban, specifically the LMH and LST serial prefix rifles. I own three of the HBAR (LMH = Law Enforcement Match HBAR) variant. The LSTs have the gov profile barrel but I only ever saw one for sale, and I was not interested given the price for the condition it was in. These came from the factory with bayonet lugs, flash hiders and A2 profile lowers instead of slabside lowers, with the latest end of the serial range getting actual front pushpins instead of the two piece screw. With the later pushpin guns, they were practically identical to an M16A2 other than markings, half moon BCG (could accept a FA BCG as there was no sear block) and the large pin trigger group (and barrel profile if HBAR). I have a short writeup/pic thread on these at Coltforum https://www.coltforum.com/threads/ban-era-law-enforcement-ar6601-ar15-a2-match-hbars.424102/ |
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Originally Posted By Apec: Actually, that would be some of the law enforcement only products Colt made during the ban, specifically the LMH and LST serial prefix rifles. I own three of the HBAR (LMH = Law Enforcement Match HBAR) variant. The LSTs have the gov profile barrel but I only ever saw one for sale, and I was not interested given the price for the condition it was in. These came from the factory with bayonet lugs, flash hiders and A2 profile lowers instead of slabside lowers, with the latest end of the serial range getting actual front pushpins instead of the two piece screw. With the later pushpin guns, they were practically identical to an M16A2 other than markings, half moon BCG (could accept a FA BCG as there was no sear block) and the large pin trigger group (and barrel profile if HBAR). I have a short writeup/pic thread on these at Coltforum https://www.coltforum.com/threads/ban-era-law-enforcement-ar6601-ar15-a2-match-hbars.424102/      |
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Originally Posted By grondike: I had no real awareness of the 20" LE rifles before I stumbled across an AR6700 with LCH prefix (Law Enforcement Competition HBAR) a while ago. Like the LMH and LST models, it has all the forbidden features along with a 1/9" HBAR barrel (dated 10/97) and removable carry handle. Mine didn't have the channel drilled for a front push pin, but I had Ken at Specialized Armament fix that for me. https://www.ar15.com/media/mediaFiles/622/c-hbar2-3631571.jpg https://www.ar15.com/media/mediaFiles/622/date2-3631570.jpg https://www.ar15.com/media/mediaFiles/622/barrel2-3631569.jpg https://www.ar15.com/media/mediaFiles/622/left2-3631568.jpg https://www.ar15.com/media/mediaFiles/622/right2-3631567.jpg I thought about having Specialized Armament do that for some of the postbans I converted, but haven’t gotten to it yet. Interesting and thanks for sharing that LCH - that’s the first I’ve seen. My theory is that the 20” law enforcement guns with full evil features were uncommon or rare because by the time the ban hit, carbines were the new trend for professional users… which is why 6520 govt carbines are a dime a dozen and the LE 20” A2s rarely show up. |
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