Hello:

I'm looking for information to decipher the "proof marks" found on AR-15 upper receivers.  Specifically, I'd like to determine the manufacturer (and date of manufacture, as applicable) of an upper from these marks.  I've searched using "proof mark" with no results.  Does anyone have a link providing a table of proof marks and the associated manufacturers (or dates), or other information?  TIA R/ Jim

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Nunquam secundum

You can go to www.biggerhammer.net, but the info listed here is dated and doesn't reflect todays, forging suppliers or manufacturers.  Very few, if any, companies use "proof stampings" on receivers now, like Colt used to with the "C" in a square and triangle near the ejection port.

More specific questions would help answer your questions.  I'm not about to type everything I know (or think I know, as I learn something new every day) in this message.

I had this saved somewhere, but don't remember where I got it


"keyhole" = Cerro
M = Marietta
C = Colt
B = Bushmaster
K = Kaiser
AF = Alcoa Forge
"bird's head" = Cardinal
broken "A" = Anchor Harvey
D which looks like a fat hollow triangle = Diemaco

ETA: modern uppers (from the '90s) that have marks just indicate who made the raw forging, not who machined and finished it.

Quoted: I had this saved somewhere, but don't remember where I got it "keyhole" = Cerro M = Marietta C = Colt B = Bushmaster K = Kaiser AF = Alcoa Forge "bird's head" = Cardinal broken "A" = Anchor Harvey D which looks like a fat hollow triangle = Diemaco

On receivers, "B" rarely, if ever, means Bushmaster.

The modern Bushmaster receivers I have seen have a broken "A" (Anchor Harvey), a keyhole with dots (Cerro Fabricating) or nothing at all (??????).

Quoted: Quoted: I had this saved somewhere, but don't remember where I got it "keyhole" = Cerro M = Marietta C = Colt B = Bushmaster K = Kaiser AF = Alcoa Forge "bird's head" = Cardinal broken "A" = Anchor Harvey D which looks like a fat hollow triangle = Diemaco On receivers, "B" rarely, if ever, means Bushmaster. The modern Bushmaster receivers I have seen have a broken "A" (Anchor Harvey), a keyhole with dots (Cerro Fabricating) or nothing at all (??????).

That is my list.  I should have clarified this more.  B is seen on Bushmaster carry handles.  On an upper, it never means Bushmaster.

These are forge marks not proof marks.

The "proof marks" you find by the ejection port on Colts are really inspection marks.  Colt quit putting them on their rifles somtime in 2000 or 2001 according to Tina at SAW.

Thanks for the info, gentlemen.  It was very informative.

Thanks, Troy, for the link to the article on upper receivers.  Based on the information in that article, it would appear that Colt has been buying AR-15 upper receiver forgings from outside sources since the early 1990's.  And worse than that, it appears that Colt has been outsourceing the machining of their forgings, and then putting the Colt name on the finished product.

The article brings two questions to mind.  How does one ensure that a rifle purchased from Colt is "all Colt"?  Also, if the article is correct, how come Colt maintains it's reputation as "The Best"?

R/ Jim

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Nunquam secundum

Quoted: Thanks for the info, gentlemen.  It was very informative. Thanks, Troy, for the link to the article on upper receivers.  Based on the information in that article, it would appear that Colt has been buying AR-15 upper receiver forgings from outside sources since the early 1990's.  And worse than that, it appears that Colt has been outsourceing the machining of their forgings, and then putting the Colt name on the finished product. The article brings two questions to mind.  How does one ensure that a rifle purchased from Colt is "all Colt"?  Also, if the article is correct, how come Colt maintains it's reputation as "The Best"? R/ Jim ---------------- Nunquam secundum

Colt has been outsourcing forgings since the 1970s

Still wondering who "C MB" is...   Colt - Mercedes Benz?


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I would like to know also. Rock River has there new mnf uppers marked this way:
                                                                                                                     C
                                                                                                                     MB



I think the C on top is Cardinal and the MB? Anyone????????????????? Thanks in advance

                                                                FF

Quoted: The article brings two questions to mind.  How does one ensure that a rifle purchased from Colt is "all Colt"?  Also, if the article is correct, how come Colt maintains it's reputation as "The Best"?

One of the basic tenants of quality control is "acceptable deviation". A component is graded as 'acceptable' or 'unacceptable' based on it's overall difference from a control sample. Each manufacturer has their own limits on the acceptable range of deviation from the control sample.

Colt maintains it's reputation as a top tier manufacturer because their acceptable range of deviation is smaller than many other commercial manufacturers. Put another way, an upper that Colt deems 'unacceptable' could very well be deemed 'acceptable' from a manufacturer that allows a higher acceptable deviation.

If you put a Colt upper next to an upper from brand X the Colt isn't necessarily better, but the chances are good that the Colt upper is dimensionally closer to the control sample than the other.

The downside to this of course is cost. If more components from a given batch are discarded then the per unit cost of 'acceptable' components become that much higher.

Another reason that Colt is considered a top tier manufacturer is that they take additional steps during the assembly and testing process that other manufacturers don't necessarily complete. Every Colt barrel and bolt for example is magnaflux particle tested and proof load fired. That's what the "MP" on a Colt barrel stands for. They also shot peen every bolt.

Some manufacturers don't take any of these extra QC steps, and some others only test samples in a specific batch, rather than every single component. Magnaflux testing is non-destructive, but it is expensive-and some manufacturers don't want to add that expense to their unit production costs.

I am surprised no one has pictures.

Sammy