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Posted: 9/4/2023 10:32:35 PM EDT
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As many of you may know, Colt produced a semi-auto rifle known as the "Gov't Model" R6550 in 1989 and 1990 which was as close as one could get from the factory to a real M16A2 rifle. Only several thousand of these R6550 rifles were ever made by Colt, and they are considered to be quite rare. By comparison, the standard HBAR rifles were much more common - the R6550 is differentiated by having a true gov't profile M16A2 barrel with the pencil diameter underneath the handguards. These rifles all have a "GS prefix" serial number and were made basically right before Colt started neutering their rifles of "evil features" in anticipation of the 1994 AWB. Since there are so few of these rifles, I though it would be useful to start a thread where people list their serial number (with an "XX" or "XXX" for the last two or three numbers) and any interesting markings or features they have on their gun. These rifles generally had small-pin, slabside lowers with no sear block and had an intact bayonet lug. My rifle, for example, (see below) has all of these features, but many later production units actually lack the bayonet lug. Furthermore, a .22 conversion kit was also included with some of these rifles and the boxes for those guns were marked R6550K - the K suffix indicating presence of the conversion kit. Please also note whether or not your gun came with the kit. Finally, note any interesting markings or anomalies in your gun. My gun, for example, has a semi-auto carrier which is unmarked - the vast majority were stamped with a "C" on the left side. My bolt has the regular Colt "MPC" markings but they are the "dot-matrix" style typical of this timeframe rather than the stamped or etched markings seen on earlier guns. As far as I know, nobody has ever done anything like this - if you have an R6550 and wish to contribute please do as we can learn a lot about this block of guns (when different features appeared/disappeared, earliest/latest reported serial number range, etc.). |
My GS rifle's serial number begins with GS0078**, it has the following characteristics. A2 Upper, with C and M on the right side of the carry handle in front of the rear sight. A1 Lower, no fence, no sear block, high shelf and AR15 style hammer, with a large two piece, screw type, front pivot pin. A2 Government profile barrel, marked C MP 5.56 NATO 1/7 A2 FSB, 0.040" lower than the F marked FSB, the bayonet lug has been removed. Colt SP1 style semi auto BCG, C marked on left side center, with MPC marked Bolt. My rifle didn't have the box or any original accessories. Rifle could be either the R6550 or the R6550K with the .22LR conversion kit missing, as some R6550s are known to have the bayonet lug removed. It would be very informative to find out where the various GS models fall serial number wise.
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My rifle has serial number GS 0050** so it is a mid-production run example. It has the following features:
Interesting note: Rifle has a standard AR15 hammer but came with an M16 safety selector (able to spin around 360 degrees and clicks into the "auto" position). I believe that this was a factory error where the guy at Colt accidentally used the wrong safety in the build. I have no reason to believe it was messed with as the gun is pristine and includes all of the original paperwork to include the 1990 dated receipt of purchase by the single original owner. Also, adding an M16 selector doesn't make any sense as the "auto" position doesn't do anything - trigger can't be pulled in that position and it is the same as the "safe" position. My rifle came with the original box and paperwork. The "green label" on the box indicated that it is an R6550K model as it originally came with the .22 conversion kit. |
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My Dad bought my rifle new in about 1990-ish? It has serial number GS 0090** so it is a late-production run example. It has the following features: A2 Upper, with C and M on the right side of the carry handle in front of the rear sight. "Slabside" no-fence lower with no sear block. Axis pins are "small-pin" diameter and receiver has the large two-piece, screw type, front pivot pin. A2 Government profile barrel, marked C MP 5.56 NATO 1/7. The barrel finish has an almost "matte-sparkle" look to it under a flashlight beam and is "ribbed for her pleasure"..... small concentric rings/ribbing/tool marks from end to end. A2 FSB with no "F mark" and no bayonet lug. Colt SP1 style semi auto carrier. Carrier is C-marked; bolt is marked "MPC" I recall seeing the "green label" on the box indicating that it is an R6550K model and I know that it originally came with the .22 conversion kit. Unfortunately, the box was discarded before I inherited the rifle. Also, Dad once told me that he had sold off the .22 conversion kit right after he bought the rifle as he saw no need for it and he thought John Ceiner was a Class-A SOB. |
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It was a LONG time before I could ever find out anything concrete when it came to GS prefix AR's. I think I originally came here [before signing up] to try and find out anything and even this site was basically a blank. Attached File |
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Quoted: It was a LONG time before I could ever find out anything concrete when it came to GS prefix AR's. I think I originally came here [before signing up] to try and find out anything and even this site was basically a blank. https://www.ar15.com/media/mediaFiles/32224/IMG_0442_JPG-2947703.JPG It came with everything save the bipod. [I bought used before the 94 ban] The sellers wife was making him sell it. Prices doubled or tripled not long afterwards and I doubt the guy put more then a mag or two through it before he sold it. |
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Quoted: It came with everything save the bipod. [I bought used before the 94 ban] The sellers wife was making him sell it. Prices doubled or tripled not long afterwards and I doubt the guy put more then a mag or two through it before he sold it. Does it have the bayonet lug intact or not? The .22 conversion kit says it may be a R6550K, if it came with the rifle from Colt. I like your setup, really looks like it could reach out and touch something. |
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Quoted: Yes - they're pretty easy to remove. I'll take it out again and wipe it down with CLP to see if anything reveals itself when damp. These are my Government Model's barrel rollmarks, nice and deep.  |
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Quoted: Can you provide the first two digits of the serial number, and key characteristics as we've started listing? Does it have the bayonet lug intact or not? The .22 conversion kit says it may be a R6550K, if it came with the rifle from Colt. I like your setup, really looks like it could reach out and touch something. Quoted: Quoted: It came with everything save the bipod. [I bought used before the 94 ban] The sellers wife was making him sell it. Prices doubled or tripled not long afterwards and I doubt the guy put more then a mag or two through it before he sold it. Does it have the bayonet lug intact or not? The .22 conversion kit says it may be a R6550K, if it came with the rifle from Colt. I like your setup, really looks like it could reach out and touch something. 0103xx. neutered carrier of the day and shaved bayo lug but past that, standard Colt AR 15 6550. No blocks or anything like that. NATO 1/7 barrel. I still have the original shaved carrier but it has a standard M16 carrier in it now which has been in for many years. It's actually [for a non flat top] pretty accurate as long as you watch for barrel cant. Didn't get the box with it but the cheekpiece, .22 conversion and mag, and ''armored'' Scope and mount are all Colt marked. The cheekpiece actually does work quite well with the scope, I took it off once and shot it and put it right back on. |
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Quoted: 0103xx. neutered carrier of the day and shaved bayo lug but past that, standard Colt AR 15 6550. No blocks or anything like that. NATO 1/7 barrel. I still have the original shaved carrier but it has a standard M16 carrier in it now which has been in for many years. It's actually [for a non flat top] pretty accurate as long as you watch for barrel cant. Didn't get the box with it but the cheekpiece, .22 conversion and mag, and ''armored'' Scope and mount are all Colt marked. The cheekpiece actually does work quite well with the scope, I took it off once and shot it and put it right back on. Original neutered BCG is a semi-auto or halfmoon? Whoa! A 10K serial number? Just to clarify, the serial prefix is GS 0103XX? This is really important information as everything I've found states the GS prefix didn't run into five digits / 10K. The highest serial number known to be in the wild is GS0092XX. The cheek riser and optic would've been accessories added by the original owner. |
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Quoted: Original neutered BCG is a semi-auto or halfmoon? Whoa! A 10K serial number? Just to clarify, the serial prefix is GS 0103XX? This is really important information as everything I've found states the GS prefix didn't run into five digits / 10K. The highest serial number known to be in the wild is GS0092XX. The cheek riser and optic would've been accessories added by the original owner. Quoted: Quoted: 0103xx. neutered carrier of the day and shaved bayo lug but past that, standard Colt AR 15 6550. No blocks or anything like that. NATO 1/7 barrel. I still have the original shaved carrier but it has a standard M16 carrier in it now which has been in for many years. It's actually [for a non flat top] pretty accurate as long as you watch for barrel cant. Didn't get the box with it but the cheekpiece, .22 conversion and mag, and ''armored'' Scope and mount are all Colt marked. The cheekpiece actually does work quite well with the scope, I took it off once and shot it and put it right back on. Original neutered BCG is a semi-auto or halfmoon? Whoa! A 10K serial number? Just to clarify, the serial prefix is GS 0103XX? This is really important information as everything I've found states the GS prefix didn't run into five digits / 10K. The highest serial number known to be in the wild is GS0092XX. The cheek riser and optic would've been accessories added by the original owner. GS 0103xx, the halfmoon piece of junk. I picked up 4 brand new Colt M16 BCM's from one of my favorite vendors back in the day [I should have bought WAY more stuff from him, he had fantastic Colt M-16 Mil stuff along with USGI M14 barrels, parts and Garand goodies. I did snag some complete uppers but I should have bought a LOT more and sold less of them. |
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Quoted: That Sir, is interesting as all hell! A five digit GS serial number. Can we get a pic of the rollmarks, please? Do you know what profile the barrel is? Quoted: Quoted: GS 0103xx, the halfmoon piece of junk. That Sir, is interesting as all hell! A five digit GS serial number. Can we get a pic of the rollmarks, please? Do you know what profile the barrel is? Barrel is standard A2 configuration. And here is the difference. It's a GS prefix but a Sporter Target Model. [which is just a gov't model from what I can tell sans bayo lug and 1/2 moon carrier] It's probably why I could never find a target model GS prefix back in the day. And Colt, well, Colt did Colt things. They never got rid of any parts. Now what makes it a target model I have no clue but it was always stupidly accurate for my shitty shooting. |
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Quoted: Barrel is standard A2 configuration. And here is the difference. It's a GS prefix but a Sporter Target Model. [which is just a gov't model from what I can tell sans bayo lug and 1/2 moon carrier] It's probably why I could never find a target model GS prefix back in the day. And Colt, well, Colt did Colt things. They never got rid of any parts. Now what makes it a target model I have no clue but it was always stupidly accurate for my shitty shooting. So is it rollmarked? Sporter Target Model Or AR-15 A2 Gov't Model |
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AH HA! Eureka! I found one, wrong prefix on a R6551 Sporter Target Model  Your Sporter is another transitional rifle from 1990. 1990 ST 0016xx, CM forge code, raised mag fence lower, large (.312) pivot, no weep hole, no sear block, std FCG, SPORTER bolt carrier, marked COLT’S FIREARM DIVISION, barrel stamped C MP 5.56 NATO 1/7 ST 001XXX CM forge code, mag fenced lower, big pivot pin, no sear block, marked COLT’S FIREARMS DIVISION (this one has a FA carrier, bayonet lug, and tear drop forward assist, maybe replacement parts?) GS 0099XX NO DETAILS GS 010173 CM forge code, slab side lower, no sear block, small hammer/trigger pins, marked COLT'S MFG CO. INC, ST 004600 and up have large trigger/hammer pins ST 005293 CM forge code, mag fenced lower, big pivot pin, no weep hole, sear block pinned on both sides, large hammer/trigger pins, marked COLT'S MFG CO. INC |
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Quoted: So is it rollmarked? Sporter Target Model Or AR-15 A2 Gov't Model Quoted: Quoted: Barrel is standard A2 configuration. And here is the difference. It's a GS prefix but a Sporter Target Model. [which is just a gov't model from what I can tell sans bayo lug and 1/2 moon carrier] It's probably why I could never find a target model GS prefix back in the day. And Colt, well, Colt did Colt things. They never got rid of any parts. Now what makes it a target model I have no clue but it was always stupidly accurate for my shitty shooting. So is it rollmarked? Sporter Target Model Or AR-15 A2 Gov't Model Sporter Target Model After the Sporter Target, didn't they go to a Sporter II? |
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Quoted: No, at least as far as I know. SPII models spanned from 1982 up to 1989, in 1988 they were phased out by the early Sporter Target Model and R6550 AR-15A2 Gov't model rifle. Quoted: Quoted: Sporter Target Model After the Sporter Target, didn't they go to a Sporter II? No, at least as far as I know. SPII models spanned from 1982 up to 1989, in 1988 they were phased out by the early Sporter Target Model and R6550 AR-15A2 Gov't model rifle. Gotcha. Thanks. When I looked years ago, I could literally find NOTHING on a GS prefix and Target Model. It was like it never existed. What was the primary differences between the Gov't model and the Sporter Target? |
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Quoted: Gotcha. Thanks. What was the primary differences between the Gov't model and the Sporter Target? The info I see online and your rifle, says it's a R6551K. Your Sporter Target Model shipped with the Colt cheek riser, optic and .22 LR conversion kit. So as far as I know the difference is those accessories and a different model rollmark. |
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Quoted: The info I see online and your rifle, says it's a R6551K. Your Sporter Target Model shipped with the Colt cheek riser optic and .22 LR conversion kit. So as far as I know the difference is those access and a different model rollmark. Quoted: Quoted: Gotcha. Thanks. What was the primary differences between the Gov't model and the Sporter Target? The info I see online and your rifle, says it's a R6551K. Your Sporter Target Model shipped with the Colt cheek riser optic and .22 LR conversion kit. So as far as I know the difference is those access and a different model rollmark. Thanks. There is little to no info out there still on this model and a search comes up with MAYBE 3-4 halfway decent hits. |
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Quoted: I tell ya, I'd have to work with a purpose to remove the rollmarks on any of my AR barrels. These are my Government Model's barrel rollmarks, nice and deep. https://i.imgur.com/X0oC682l.jpg Quoted: Quoted: Yes - they're pretty easy to remove. I'll take it out again and wipe it down with CLP to see if anything reveals itself when damp. These are my Government Model's barrel rollmarks, nice and deep. https://i.imgur.com/X0oC682l.jpg My bad - post edited. I was looking under the handguards and there it was all along plain as day out in front of the FSB. A2 Government profile barrel, marked C MP 5.56 NATO 1/7. The barrel finish has an almost "matte-sparkle" look to it under a flashlight beam and is "ribbed for her pleasure"..... small concentric rings/ribbing/tool marks from end to end. Attached File More pron for your viewing pleasure: Attached File Attached File Attached File |
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Gentlemen, excellent work - this is definitely an interesting batch of rifles! I should also note that my carrier is indeed the SP1-style part and not the much later half-moon carrier. Another thing I noticed - my handguards are unmarked inside on the metal heat shields. I know that the later A2 handguards were marked "DO NOT REMOVE" on the inside - I wonder when that change was made and if any "GS" prefix rifles were shipped out with the later style handguards. Also, if we get enough data through this thread we could probably figure out around what serial number the bayo lugs started getting shaved off. |
I have a Colt AR-15A2 gov’t model with serial number GS009713. I just have the rifle, no box or paperwork, but it has an A1 style upper receiver with 20” barrel. The FSB has a bayonet lug and is not F marked. I cannot find any markings on the barrel other than a “C” on the bottom of the barrel behind the muzzle device and MP on the right side of the barrel under the FSB. No visible markings on the BCG. 
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Quoted: I have a Colt AR-15A2 gov’t model with serial number GS009713. I just have the rifle, no box or paperwork, but it has an A1 style upper receiver with 20” barrel. The FSB has a bayonet lug and is not F marked. I cannot find any markings on the barrel other than a “C” on the bottom of the barrel behind the muzzle device and MP on the right side of the barrel under the FSB. No visible markings on the BCG. https://imgur.com/a/7ZqMxed This is an extremely interesting rifle! Do you think that it left the factory in this configuration? If so, then it really would lend credence to the theory that Colt assembles these GS prefix rifles out of a pretty wide assortment of parts they had on hand. |
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I’ve had my R6550 for over 20 years now. It’s in the configuration described in the OP with the bayonet lug. Serial number GS0068XX IMO, one of if not the best rifles Colt made. On the right. Attached File |
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Quoted: I’ve had my R6550 for over 20 years now. It’s in the configuration described in the OP with the bayonet lug. Serial number GS0068XX IMO, one of if not the best rifles Colt made. On the right. https://www.ar15.com/media/mediaFiles/9341/IMG_0108_jpeg-2954212.JPG Nice rifle! Would you be able to tell us a bit about the markings on the bolt and carrier? If you could post pictures, that would also be great. |
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