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Posted: 5/3/2003 11:04:17 PM EDT
[Last Edit: 5/3/2003 11:07:55 PM EDT by M4-guy]
I just bought a new flat top upper and am wondering exactly what I have. I've read the many posts on distinguishing cast lowers from forged, but how can you determine if an upper receiver is forged or not? Is there even such a thing as a cast upper?

I was told the upper was a Bushmaster, but it has some unfamiliar markings. There's a keyhole mark behind the brass deflector. And the slots are even numbered 2 through 12 from the rear going forward. What did I buy???
Link Posted: 5/4/2003 5:22:48 AM EDT
That's the mystery upper receiver! I've seen them on RRA's most frequently, less so on BMs, and rarely on Colts. They're excellent receivers. I even bought one just to have on hand for any future build projects I might undertake. They're available from Pete in NH and Steve at Adco. Might be worth a call to hear what they have to say regarding their origin.
Link Posted: 5/4/2003 6:04:19 AM EDT
How is the machining inside the loop of the carry handle? Is there any seam left to be seen? The seam on a cast part is very narrow, think pencil line thickness. The seam on a forged part is thick, around ¼" wide. This applies to anything cast vs. forged, not just AR receivers. But many times the seam is machined away and so it's harder to tell. I don't have any idea if there are any cast upper receivers available.
Link Posted: 5/4/2003 9:40:35 AM EDT
May give you some clues for an upper too: http://www.olyarms.com/castorforged.html
Link Posted: 5/4/2003 3:00:52 PM EDT
The only cast upper receiver I know of is on the Olympic Arms Plinker. The way to tell is the surface is rougher than a forged receiver and it's a A1 design. It's also not machined out at the rear of the carry handle. Here is an Oly cast upper: [img]http://www.gunsnet.net/album/data/500/6201A1upper-med.jpg[/img]
Link Posted: 5/4/2003 10:16:38 PM EDT
Thanks for the info. Sorry if I didn't make it clear, but this is an A3 (flattop) upper. I should also mention that it seems to be of excellent quality. The slot numbers are etched/forged into the receiver and appear to have been done with a great degree of precision. I've compared this upper with my BM A1 and A2 uppers, and I'm almost sure it's forged.
Link Posted: 5/5/2003 3:20:41 AM EDT
It most likely is. Like I said Oly is the only mfgr I know who makes a cast upper. If it has the same exterior finnish as your forged lower then it's forged. Another indicator that it's forged would be the fact that it IS a A3 flattop upper with rail markings. I wouldn't worry about it.
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