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Droppin Deuces
10-19-2010, 2:50 PM
http://www.calguns.net/calgunforum/showthread.php?t=353726

I posted this in the gunsmithing/how-to forum, but am getting no love. I figure there must be someone in centerfire(the official AR forum) who will know.

Thanks!

crob
10-19-2010, 3:07 PM
I believe the keyhole marking indicates Cerro Forge. By no means an expert, but that bit of info seems have been put into my head from somewhere. As for the square, I have no idea

Edit, some quick google research shows the square is the mark for brass aluminum forgings. What that means, I have no idea. Now if you want to take it further, you have some starting points

Pryde
10-19-2010, 3:07 PM
They are proof marks from forging houses where the raw aluminum forgings are made. The keyhole is Cerro Forge, another common one is Cardinal Forge (Bird's head), Alcoa Forge (AF) and the square is Brass Aluminum Forgings.

Each manufacturer of carrying handles and upper receivers buys the raw forgings and finishes them by machining them and adding all the proper parts such as the rear sight, ejection port cover and forward assist.

The fact that there is a mark on them just proves that the handle/receiver was made of forged aluminum. Each manufacturer has their own standards for the finished machining and the parts quality. For example a Colt upper receiver and a DPMS upper receiver may have the same proof mark like the keyhole but the overall quality of the part will be different based on the manufacturer's specifications.

Droppin Deuces
10-19-2010, 5:48 PM
Got it, thanks so much for explaining that, guys!