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Thread: Billet Upper and Lower Made Of 6061 Aluminum?

  1. #11
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    Quote Originally Posted by Clobbersauras View Post
    This has been nagging at me for a while. I'm hoping the quality of debate is better here and that members have some firm data or insights on this topic. We all know that 7075 is more durable, but is it really necessary in this application?
    the upper and lower arent the primary stress components. When a round is fired the bolt, barrel, and barrel extension take all all the force. The upper is essentially a housing to hold the barrel, gas tube, charging handle and bolt carrier group, thats why its made out of aluminum and not steel.
    Last edited by ForTehNguyen; 11-14-11 at 23:59.

  2. #12
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    Maybe not primary, but still important.

    There was a high speed video on YouTube where you could see the upper flex with each shot.

    In theory, as long as any flex action was repeatable, it flexed the same and returned to te same position everytime, this wouldn't effect group size in the short term. Over the long term, maybe there's a fatigue issue. Again, just theory.

    For any accuracy based upper, I would only use a Vltor receiver. Of course the trade off is cost and weight over a standard forging. But you get what you pay for...

  3. #13
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    7075 aluminum has a harder surface than 6061 Especially when anodized, 7075 has a much harder surface. With 6061, threads are softer which makes them easier to cross thread and will distort at a lower torque. Trigger pin holes will wallow out faster

    While 7075 is harder than 6061, machine tool life is still good When machined before heat treating, aluminum alloys are very easy to machine. Even after heat treating, aluminum is a breeze to machine compared to steel

    7075 is stiffer than 6061 During firing, 7075 will flex less than 6061. 7075 also is less ductile and less prone to bending

    Receivers made of 6061 are billets I do not know of any 6061 receivers that are machined from forgings. Billet receivers cost more and pound for pound are weaker than forged.

    7075 is a better alloy for making forgings Receivers are made from 7075 forgings because they cost less, have greater strength, are more rigid, offer greater durability of threads and trigger pin holes, than any receiver made from 6061, not because of some antiquated material specification

    Buying a receiver made of 6061, especially made from a billet, is paying more for less and makes no sense
    Last edited by MistWolf; 11-15-11 at 07:19.
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  4. #14
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    If you're really curious,

    Seeing as some like to say aircraft grade this or that..

    http://www.aircraftspruce.com/catalo...s/aluminfo.php

  5. #15
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    Quote Originally Posted by MistWolf View Post
    Buying a receiver made of 6061, especially made from a billet, is paying more for less and makes no sense
    End of STORY!

    This is why the military uses Forged receivers....

    A beat to hell Mil Upper before restore/rebuild..
    "You people have too much time on your hands." - scottryan

  6. #16
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    7075 is a significantly superior material I have used and machined both 6061 and 7075 tool wear is almost a non factor when using either material. Also, we find 7075 easier to machine because it is less gummy than the 6061. However, 7075 sells for less with the scrap man due to it being less pure than 6061.

    7075 Mechanical Properties
    Hardness, Rockwell 53.5
    Ultimate Tensile Strength 83000 psi
    Tensile Yield Strength 73000 psi
    Elongation at Break 11 %

    6061 Mechanical Properties
    Hardness, Rockwell 40
    Ultimate Tensile Strength 45000 psi
    Tensile Yield Strength 40000 psi
    Elongation at Break 12 %

  7. #17
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    My guess?

    I'm assuming this is why Clobb asked the question here:

    http://northeasternarms.com/platforms-1

    Asking the question on Canadiangunnutz will at best get you jumped by the NEA fanboys, and banned at worst.

    For me, the question is answered above by a combination of what mistwolf and mrwetwork posted. It may not be required, but why use parts made from 6061 billet, when you can have 7075 forgings for not much more. Looking at those figures, I mean wow!

    Regards.

    Mark

  8. #18
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    Actually, that question has been asked on CGN. No bans were instituted.

    I know because the discussion occurred in my thread, where I started talking about the NEA guns, back before the project was common knowledge.

    I commented on this exact issue myself, and said that I had a hard time taking 6061 when 7075 was the standard. I consider it a step down in materials strength and whether it matters or not, I don't like it.

    And nobody gave me a hard time about it at all.

    And Greentips (owner of the site for those who don't know) talked about it extensively, and said he'd rather have 7075. He did not seem interested in banning himself afterwards but it is difficult to say for sure.

    At any rate, I am interested to hear continued debate on 6061 vs 7075, but I don't think there is all that much of a debate. 7075 is preferred. 6061 is probably adequate and I believe that older Colts were made of 6061.

    But I would take 7075 if I could. There is always the option of swapping out the upper, of course.

    But it frustrates me that NEA has chosen to go with 6061, even if their reasoning is correct. Their position is that their engineers have determined that 6061 is a good material for their demands, and that 7075 is unnecessary and I don't doubt that they have a point. But I have a hard time taking a step down in materials strength, necessary or not.
    Full disclosure: I'm the editor of Calibre Magazine, which is Canada's gun magazine. In the past I've done consulting work for different manufacturers and OEM suppliers, but not currently. M4C's disclosure policy doesn't seem to cover me but we do have advertisers, although I don't handle that side of things and in general I do not know who is paying us at any given time.

  9. #19
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    Thread hijack...

    It's not so much asking the original question, but calling out a forum sponsor when they respond with the marketing BS and outright garbage that I have seen posted on CGN probably will. But that would, and has, happened on TOS and other similar forums too.

    Do you think they would get away with some of their replies here, or better yet, forums like LF?

    I'm not interested in turning this thread into a CGN/NEA bashing exercise, as quite frankly I would never purchase one of their rifles, and I don't care how other people choose to spend their money, but I do have a severe allergy to BS.

    End of thread hijack.

    Regards.

    Mark

  10. #20
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    Quote Originally Posted by misanthropist View Post
    Their position is that their engineers have determined that 6061 is a good material for their demands, and that 7075 is unnecessary and I don't doubt that they have a point. But I have a hard time taking a step down in materials strength, necessary or not.
    Assuming that the firearms are used exactly as intended there is no issue with 6061. For example... dry firing a complete lower receiver that is made of 7075 will result in almost 0 deformation of the metal between the FCG and the bolt catch. Whereas with 6061 there will be immediate deformation in 10-15 fires. The metal there is only ~.093 thick. Does that affect the performance? No, there is plenty of clearance on both sides and if you dry fire with it in complete rifle configuration the firing pin/bcg limit the hammer from smacking that wall.

    Also, from a production aspect when making these out of billet it costs you roughly 100% more to manufacture from 7075 than 6061. Most companies do not have the coin to make a mold for 7075 forgings.

    My favorite thing about the AR-15 is that most of the parts are not under heavy stress. It is a very smooth system. The upper receiver really is just a housing to allow the bcg to move about. As is the buffer tube. There are no real extreme forces going on there. The most extreme forces are in the chamber, through the gas port and into the gas block where they start bleeding off.
    Last edited by mrwetwork; 11-15-11 at 14:25.

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