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Thread: Billet Upper and Lower Made Of 6061 Aluminum?

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    Billet Upper and Lower Made Of 6061 Aluminum?

    I know 7075 is the standard for AR uppers and lowers. But is this standard really needed to ensure the proper function and longevity of the rifle? Do the uppers and lowers need to be made of 7075 or is it just a waste of more expensive alloy? Would a properly coated and machined 6061 hold up just as well?

    Your thoughts greatly appreciated.
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    From everything that I have read and experienced 7075 is far superior to 6061 in terms of strength and wear. Uppers and lowers seem to outlast almost every other component, so why skimp? At the most you would save what, $60 - $80 for an entire rifle?

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    I am of the opinion that the quality of the machine work is more important than the difference between 7 and 6 series aluminum.

    That being said, you can get a Vltor upper which is made from a 7 series forging and is amazingly accurate in its dimensions. Perfect alignment to a DD RIS-II, and no windage correction needed when used with a Noveske barrel and a Short Dot in a Larue mount.

    When you use parts which are dimensionally perfect, it's much easier to zero your weapon.

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    ^^That's an interesting statement.

    I'm just wondering about the typical wear points in the upper receiver and the pin holes in the lower. Is the use of 7075 just a hold out from an antiquated military spec?
    Last edited by Clobbersauras; 11-14-11 at 21:42.
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    Quote Originally Posted by Dunderway View Post
    From everything that I have read and experienced 7075 is far superior to 6061 in terms of strength and wear. Uppers and lowers seem to outlast almost every other component, so why skimp? At the most you would save what, $60 - $80 for an entire rifle?
    It wouldn't matter much to most consumers but it would matter greatly to the manufacturer where profit margins are thin. If using 6061 is cheaper with no loss in performance of the rifle, then it's a sound business decision.
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    The 6 series is easier on the tooling too. Harder metals eat tooling like crazy.

    This was my 50 yard zero target with 5.56mm TAP. No windage correction.

    Next range trip I'm going to move to a 100 yard zero.



    I will only use Larue or Vltor uppers. Being dimensionally accurate is much more important that material difference.

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    While it IS true that fit and finish are paramount, the rigidity of an upper made of 7075 is much greater than an identical design of 6061. The lower also benefits, ever look at the area where the receiver extension threads in? Thin cross sections like that gain significantly by being a superior alloy.
    Sure a 6061 model will probably suffice in most situations but material costs and tooling life don't warrant the compromise in my opinion.
    Now Forged vs. Billet...

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    Interesting thread, from a Canadian perspective at least. Of course I have no idea what generated this question...

    I suspect it is a non-issue but I struggle with this as well. Instinctively my reaction to the use of 6061 is bad.
    However, properly treated, I wonder if the 6061 really gives up all that much?

    My concerns may be more based in the fact that typically, companies that have used these materials have cut corners that really DO matter.

    Much like the finish under the FSB...it may not matter at all from a user perspective, and simply be indicative of a company which, generally speaking, doesn't give a shit. But if a company does everything else bang on, are you going to avoid them because they don't think there's a point to putting a finish on the barrel before they mount the FSB?

    Anyway, hopefully some more materials-expert people will give their thoughts.
    Last edited by misanthropist; 11-20-11 at 14:50.
    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.

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    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?
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    Its a buyers market. I would choose 7 series over 6 series, and forged over billet.

    The only way I would take a 6 series billet over a 7 series forged, provided machining was equally high quality, was if the 6 gave me some feature I had to have. But I don't think such a situation exists. I don't even really see a significant cost difference between the two.

    You can get a Vltor upper which is perfectly machined off of a 7 series forging.

    Barrel steel...that's amost another thread. If its 416, 416R, 4140, LW50, CMV or the like, everyone will have tons of reason to tell you why theirs is the best. Again, I think this comes down to what the finish manufacturer is doing, provided the blanks they get are of high quality.

    Some of the material content effects how the barrel is machined, life of the tools use etc. If one barrel can be machined easier with a better finish, it may be a result in a better product and an improved price point.

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