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Posted: 12/6/2002 4:20:08 PM EDT
Of course forged upper and lower is next thing to stainless, however I feel a cast lower and forged upper is as good. The real stresses from firing are on the upper not the lower.

Well am I full of it or what?

I know I am usually but I mean on this topic.
Link Posted: 12/6/2002 5:09:50 PM EDT
I'll concur. I don't see a problem with cast, sans running it over with a car or something. Cast aluminum can be quite brittle, but I just don't think it's an issue as far as shooting stresses go.
Link Posted: 12/6/2002 5:21:10 PM EDT
a casting should work just fine. but they are just uglier than a forging
Link Posted: 12/6/2002 5:25:00 PM EDT
I would tend to agree with your assessment.
Link Posted: 12/7/2002 7:09:36 AM EDT
If you have an unmarked upper, any way to tell which it is? DoorKicker6
Link Posted: 12/7/2002 10:36:43 AM EDT
You can tell the differance quite easily. The forged part is smooth as a babies butt and the cast feels rough like it needs a shave. The forged uppers I have seen are a bit darker black due to the coating being smoother while the cast is porus. One thing I can tell you is that if you can't tell the differance then whatever you have is same upper an lower for the diff is obvious.
Link Posted: 12/7/2002 10:15:00 PM EDT
Originally Poted By PeteCO: Cast aluminum can be quite brittle, but I just don't think it's an issue as far as shooting stresses go.
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"Brittle?" How can it be brittle? A forging is more brittle than a cast...'
Link Posted: 12/8/2002 12:05:06 AM EDT
[Last Edit: 12/8/2002 12:06:31 AM EDT by QCMGR]
Originally Posted By budam:
Originally Poted By PeteCO: Cast aluminum can be quite brittle, but I just don't think it's an issue as far as shooting stresses go.
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"Brittle?" How can it be brittle? A forging is more brittle than a cast...'
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Please explain how you came to that conclusion.
Link Posted: 12/8/2002 10:41:08 PM EDT
Originally Posted By QCMGR: "Brittle?" How can it be brittle? A forging is more brittle than a cast...'
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Please explain how you came to that conclusion.
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I am waiting for the initial person to explain their brittle theory. Just remember, in general, the harder something is the more brittle it becomes. With alloy's we modify the point where a metal becomes brittle, but to keep making XYVZ metal harder and harder, it will become more brittle.
Link Posted: 12/8/2002 11:13:24 PM EDT
[Last Edit: 12/8/2002 11:17:03 PM EDT by ProfGAB101]
I'm pissed right now cause I had a huge reply typed and the ARFCOM server logged me out and wiped the post... This is getting ridiculess Most cast items are made using [url=http://www.matls.com/search/SpecificMaterial.asp?bassnum=MAC35Q]A356T6[/url] - this is due to its grain structure more brittle than [url=http://www.matls.com/search/SpecificMaterial.asp?bassnum=MA7076]7075T651[/url] which is the alloy most common for AR forgings. The T# referes to current hardness and temper state. While the cast items [u]can[/u] be further heat treated to improve there grain structure and physical properties most mfg don't because of the high chance of warpage. Most often the parts are machined as cast. Note: the above link for 356 is listed as sand cast. Most AR related parts would not be sand cast, they would be investment cast AKA lost wax. Forged frames have a more ductile grain structure and therefore are less brittle than a cast frame. BTW - I have made over 100 investment cast AR frames. They are well up to the task.
Link Posted: 12/9/2002 10:59:46 PM EDT
Originally Posted By ProfGAB101: Forged frames have a more ductile grain structure and therefore are less brittle than a cast frame. BTW - I have made over 100 investment cast AR frames. They are well up to the task.
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I went back and did the research and the Prof is correct. My apologies for the confusion. I had to go look up the definition of brittle to see that I was defining it incorrectly. Thank you for taking the time to clarify my mistake.
Link Posted: 12/10/2002 5:44:35 PM EDT
Link Posted: 12/10/2002 9:45:10 PM EDT
Originally Posted By budam:
Originally Posted By ProfGAB101: Forged frames have a more ductile grain structure and therefore are less brittle than a cast frame. BTW - I have made over 100 investment cast AR frames. They are well up to the task.
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I went back and did the research and the Prof is correct. My apologies for the confusion. I had to go look up the definition of brittle to see that I was defining it incorrectly. Thank you for taking the time to clarify my mistake.
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What I tell ya! Next time don't question me until you do your homework! [;)]
Link Posted: 12/12/2002 1:51:30 PM EDT
Uh, yes look here: http://www.ar15.com/forums/topic.html?b=1&f=74&t=155892 This was my weapon. It now belongs to Olympic Arms. I am still waiting to recieve my M4 marked with the same # as the plinker. Any questions you can E me.
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