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Posted: 5/10/2009 10:04:00 PM EDT
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I bough this upper which was sold as a Colt upper. Barrel is the skinny 16" with C MP 5.56 NATO 1/7 with A2 flashhider and crush washer. Barrel is marked 02/07 under the handguards so it's a pretty recent barrel. FSB is marked diamond shape 2, handguards look like Colt ones I've seen before. the barrel assembly I'm pretty sure is Colt.
Now the upper receiver is where I have some doubt. I know most Colt uppers are proof marked C, this just has the Cerro keyhole forging mark. Has Colt released uppers where they haven't proof marked them with a C? Does the M4 markings above the gas tube and T-Rail markings look correct for a Colt? It does have tiny anodized m4 feed ramps cut into the receiver. What do you guys think? Factory Colt upper or Colt barrel put on a Cerro upper? What Colt model would this upper correspond to? 16" lightweight "skinny" barrel on A3 upper. 
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Most Colt barrels on flat top upper receivers have a "F" marked FSB, if yours doesn't probably it came from a model 6520 A2 fixed carry handle Gov't. carbine with an A2 type FSB.
The font of your "M4" marking is different as mine, mine looks exactly like the pic from member Frens. I'm not aware of any lightweight carbine model with a flat top from the factory. I would guess that someone installed a Colt 6520 barrel on a different brand flat top upper. |
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I bough this upper which was sold as a Colt upper. Barrel is the skinny 16" with C MP 5.56 NATO 1/7 with A2 flashhider and crush washer. Barrel is marked 02/07 under the handguards so it's a pretty recent barrel. FSB is marked diamond shape 2, handguards look like Colt ones I've seen before. the barrel assembly I'm pretty sure is Colt. Now the upper receiver is where I have some doubt. I know most Colt uppers are proof marked C, this just has the Cerro keyhole forging mark. Has Colt released uppers where they haven't proof marked them with a C? Does the M4 markings above the gas tube and T-Rail markings look correct for a Colt? It does have tiny anodized m4 feed ramps cut into the receiver. What do you guys think? Factory Colt upper or Colt barrel put on a Cerro upper? What Colt model would this upper correspond to? 16" lightweight "skinny" barrel on A3 upper. http://i43.tinypic.com/2lurnkn.jpg http://i40.tinypic.com/10ompkx.jpg http://i41.tinypic.com/2a8gpjr.jpg http://i43.tinypic.com/2625ft3.jpg This one looks identical to the upper I purchased from BCM. They just list them as "gov't contract" uppers but there is some speculation that they are produced by CMT. |
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I bough this upper which was sold as a Colt upper. Barrel is the skinny 16" with C MP 5.56 NATO 1/7 with A2 flashhider and crush washer. Barrel is marked 02/07 under the handguards so it's a pretty recent barrel. FSB is marked diamond shape 2, handguards look like Colt ones I've seen before. the barrel assembly I'm pretty sure is Colt. Now the upper receiver is where I have some doubt. I know most Colt uppers are proof marked C, this just has the Cerro keyhole forging mark. Has Colt released uppers where they haven't proof marked them with a C? Does the M4 markings above the gas tube and T-Rail markings look correct for a Colt? It does have tiny anodized m4 feed ramps cut into the receiver. What do you guys think? Factory Colt upper or Colt barrel put on a Cerro upper? What Colt model would this upper correspond to? 16" lightweight "skinny" barrel on A3 upper. http://i43.tinypic.com/2lurnkn.jpg http://i40.tinypic.com/10ompkx.jpg http://i41.tinypic.com/2a8gpjr.jpg http://i43.tinypic.com/2625ft3.jpg  Dammm I be mad if this isn't a Upper COlt Rec..and swap w/ the colt barrier. All Colt parts are branded..Take it back and refund the differences.
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thanks for the input. that's kind of what i thought when it wasn't proof marked but the lack of the F on the FSB gave it away. i got it in a trade and since barrels are hard to come by, especially a lightweight 1/7 colt barrel and the upper seems to be of decent quality, i'll keep it as a shooter.
barrel pics. 
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I would just like to add since you have a lower A2 FSB on a flat top upper you might need a taller 0.040" front sight post if you can't lower your grouping when you zero it.
The taller front sight post are available from Bushmaster, m-aparts.com and other parts dealers. |
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btw, unless you paid big money for that upper I wouldnt really care about the receiver being "original" Colt or not because Cerro forge receivers are/have been used by Colt 
the only difference is the C marking Good point, it appears to be a good quality receiver from CMT or BCM maybe, and the feedramp cuts match up to the barrel extension well, so I wouldn't worry about it. ETA: It's probably a pretty damn handy upper setup with the lightweight barrel and flat top upper. |
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I bough this upper which was sold as a Colt upper. Barrel is the skinny 16" with C MP 5.56 NATO 1/7 with A2 flashhider and crush washer. Barrel is marked 02/07 under the handguards so it's a pretty recent barrel. FSB is marked diamond shape 2, handguards look like Colt ones I've seen before. the barrel assembly I'm pretty sure is Colt. Now the upper receiver is where I have some doubt. I know most Colt uppers are proof marked C, this just has the Cerro keyhole forging mark. Has Colt released uppers where they haven't proof marked them with a C? Does the M4 markings above the gas tube and T-Rail markings look correct for a Colt? It does have tiny anodized m4 feed ramps cut into the receiver. Just for a little clarification, the "C" that you are referring to is not a proof mark. It is a forge mark. Colt proof marks are shown below. 
Shown below are some of the various forge marks found on genuine Colt flat-top upper receivers. 
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| thanks for all the input. i wasn't particularly concerned, just curious since the seller had said it was colt and that sometimes they aren't marked. it's a good forging and i like the lightweight barrels and don't really like the a2 uppers so this is perfect for me. |
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I've looked for what the A C marked upper is and I can't find it. Anyone know? A C = A (splintered) = Anchor Harvey Aluminum & C = Colt Other forge markings: AF = Alcoa Forge C AF = Colt/ Alcoa Forge C MB = Colt/ Mueller Brass Cardinal (stylized bird head) = Cardinal Forge CH = Colt/ Harvey Aluminum CK = Colt/ Kaiser Aluminum CM = Colt/ Martin Marietta D (stylized) = Diemaco Colt Canada DK = Diemaco/ Kaiser Aluminum Square (symbol) = Brass Aluminum Forging Enterprises |
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I've looked for what the A C marked upper is and I can't find it. Anyone know? "Anchor-Harvey" and "Colt". Thanks, are they common? What? You want an uncoomon forge mark so it'lll be worth more money?? 
They're ALL common. Colt, and everyone else, all use the same batch of forges; and at any given moment, they'll all buy from which ever forge is turning out blanks that week (month?, year?) These forges make a hell of a lot more things than AR15//M16/M4 blanks; so where the makers get their blanks at any time is just a function of who is in production of them at the moment.
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