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Thread: Polymer lowers

  1. #31
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    The Cav Arms lowers are an example of what happens if you engineer a lower to be made out of plastic. From what I've seen, as long as you get one that was welded together properly, they are solid and reliable.

    For the minor price difference, though, I don't see an advantage (unless you want to run a .45 upper).

  2. #32
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    Quote Originally Posted by maindish View Post
    Thank you,
    This was a much more efficient way to make the point I meant to make. I'm an engineer, we are good at understanding such things, but have to work extra hard to communicate properly.

    A good polymer receiver should be darn near a ground-up design, constrained by the critical internal dimensions and parts compatibility.

    I'll try again: aluminum does not make it good, polymer does not make it bad. Good design and practices make it good, bad makes bad.

    It always grinds me when people are so goddam smart about aluminum receivers also, with things like this:

    -"billet receivers are better" Are they? What is the material, alloy, and heat treatment? What areas have been strengthened to surpass the strength provided by forging? Did you get an extra special Zombie logo machined into the 6061 "aircraft aluminum" magwell?

    -"Forged receivers are the best" What's your application? How long and heavy is your barrel? Are you mounting optics? For example, I've been seeking Vltor MUR or Mega billet uppers to do a couple of builds with heavy barrels, long-range, large optics. The point here is stiffness from bore to scope. The military "flat-top" A3 upper is made for a gun with a relatively lightweight, 14.25" barrel and 1x optics or irons.

    -"If it doesn't have a dancing horse on it, it had better say BCM or it's crap" I have lots of respect for those brands, who are committed to quality control and reputation. However, nearly all of the brands by forged blanks from the same small group of forging suppliers. If these are CNC-machined to within the tolerances, the receivers will be functionally equivalent.

    Of course, the world is full of people who spend $30K on a car and start replacing functional components with chrome parts off of ebay, you know, because us engineers are a bunch of f'n idiots and didn't make good choices.
    I hear you. I'm a quality guy and people on here look at me like I have a dick growing out of my forehead for suggesting that there's nothing wrong with batch testing BCGs and that 4140 vs 4150 is mostly irrelevant for civilian and LE applications...


    I could see this happen in the future for sure as the technology and manufacturing processes become more refined. I think in similar fashion to the Glocks where they fuse the metal slide rails into the poly frame we will see this happen with trigger pin holes and receiver extension threads becoming a metal insert.
    The technology exists, it's just that no one besides Cav Arms or GWACS has really tried to make a high quality product for the M16 FOW yet. Hell, FN did it with the SCAR. Most of the polymer stuff out there is from small players trying to make a quick buck on a poorly designed (for hard use) product like all the ones that seem to be an injection mold of an alloy lower. Imagine a polymer lower with an integrated Magpul MOE Rifle Stock, PRS or UBR?
    Quote Originally Posted by Jaykayyy
    And to the guys whining about spending more on training, and relying less on the hardware, you just sound like your [sic] trying to make yourself feel superior.

  3. #33
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    Quote Originally Posted by jaxman7 View Post
    If NASA did an AR lower then it would have to some how perform an outreach service to the Muslim community.

    -Jax
    Thought better of the joke... too late to delete
    Last edited by Grizzly16; 03-21-13 at 11:36.

  4. #34
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    Quote Originally Posted by markm View Post
    For a dedicated rimfire... maybe.

    Even then, I wouldn't take one for FREE. No joke.
    If someone offers you a FN SCAR for free, with it's crappy polymer lower, and you don't want it, please send them to me. I will give you a $100 finder's fee and save you from the misery and embarrassment of having a plastic lower.

    Others have made the point here: polymer "AR-style" rifles will stick around and some will be nothing like the Bushmaster Crapbon 15.
    Someday far in the future engineers may even laugh at our crude metal guns, with their high manufacturing cost, limited geometry, etc.

  5. #35
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    Quote Originally Posted by maindish View Post
    If someone offers you a FN SCAR for free, with it's crappy polymer lower, and you don't want it, please send them to me. I will give you a $100 finder's fee and save you from the misery and embarrassment of having a plastic lower.
    I'll take the thing an put it on the Auctions.

    Others have made the point here: polymer "AR-style" rifles will stick around and some will be nothing like the Bushmaster Crapbon 15.
    Someday far in the future engineers may even laugh at our crude metal guns, with their high manufacturing cost, limited geometry, etc.
    Until that day.... I stand by my policy. I've yet to see one polymer AR15 receiver that I'd trust to do anything.
    "You people have too much time on your hands." - scottryan

  6. #36
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    Unless is a ground up effort/redesign like the calvary arms one With integrated grip, buffer tube/stock i don't really see the point of polymer lowers vs forged AL lowers on centerfire ARs. The one time cost savings are negligible,weigh is only a bit less but almost all of them have record of cracking. Not worth the risk IMO.

    Dedicated polymer lovers like SCAR are a whole other matter, they are fin just as a glock poly frame.

    Now, imagine what could magpul do I the got into AR polymer lower business.
    Last edited by grunz; 03-21-13 at 16:29.

  7. #37
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    Just because a polymer AR lower can be made right, doesn't mean any have. All the current polymer AR lowers are made the same and have the same flaws. When someone steps up and places metal inserts in their polymer lower, like the pistol makers have done with pistol frames, then it will be right.

    Until that day, polymer AR lowers will remain a decorative novelty
    Last edited by MistWolf; 03-21-13 at 16:28.
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  8. #38
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    Different guns for different purposes is the main point I'm trying to make. I've had quite a few people ask me to build for them and end up with a New Frontier due to sticker shock. Some of them very quickly end up buying quality ARs and being political/financial supporters of an industry they previously had no interest in. There's no reason to embarrass them while they are still in the crib.

    Technically, plastic=bad and metal=good is just not an accurate catchall statement, even if the generalization can be supported by past examples.

    However, you will do very well in your SCAR auction these days!
    Last edited by maindish; 03-21-13 at 17:02. Reason: grammar and spelling like an idiot

  9. #39
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    Quote Originally Posted by maindish View Post
    Different guns for different purposes is the main point I'm trying to make. I've had quite a few people ask me to build for them and end up with a New Frontier due to sticker shock. Some of them very quickly end up buying quality ARs and being political/financial supporters of an industry they previously had no interest in. There's no reason to embarrass them while they are still in the crib.
    Wow well said! Someone mentioned the complete plastic 15-22. Some of us still like some metal which is why I went with the sig 522.
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  10. #40
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    Why is FN the only company that can make a reliable polymer lower?

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