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Thread: Polymer Lower Receivers? Final Verdict.

  1. #21
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    Quote Originally Posted by HHollow View Post
    I am a polymer engineer and I love plastics of all kinds. I agree that a polymer lower would hold up (longer) if designed from the ground up. However, I would not use polymers on anything I would need to still be functional after 20 years. Polymer simply does not age well. Oxidizes, stress cracks, embrittles, light induced decomposition, plasticizer migration, etc. Many folks who make thinks out of commercial polymer formulations have no idea what research is really necessary to show long term durability.
    I certainly know of polymer items that literally fell apart in 20 years or less, but also know plenty of polymer items far over 20 years old that are going strong. Glock pistols and mags for instance.

    Andy

  2. #22
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    Quote Originally Posted by AndyLate View Post
    I certainly know of polymer items that literally fell apart in 20 years or less, but also know plenty of polymer items far over 20 years old that are going strong. Glock pistols and mags for instance.

    Andy
    Agreed that some larger companies can spend the time and money necessary to develop the right polymer for an application. Auto companies do this as their reputation and liability are a concern. For small mom and pop applications the is no long term testing and formulations will not be custom.

    I wager that the Glock frames are made out of a polymer formulation developed at great expense and for that targeted application.

  3. #23
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    In theory I don't see why solid polymer AR lowers can't be made given that Glocks, Sigs, etc. make solid pistol frames that hold up very well, and those have reciprocating slides unlike rifle lowers.

  4. #24
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    Quote Originally Posted by GSPatton View Post
    In theory I don't see why solid polymer AR lowers can't be made given that Glocks, Sigs, etc. make solid pistol frames that hold up very well, and those have reciprocating slides unlike rifle lowers.
    It needs major structural reinforcement at the buffer tower; personally, if I was designing a poly lower I'd raise the top-line to wrap around the bottom half of the upper so you have a new structural member joining the whole taco from buffer tower to pivot pin. Notch it just enough to clear the assist, deflector and bolt catch, and make the new reinforcement at least 1/8" if solid material. Ideally, I'd want my poly-AR done as a plastic casting around a metal buffer-ring, top-frame to include pivot/TD pin sockets and back-end down to the grip mount, basically a metal load-bearing section with a plastic trigger-pocket and magwell.
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  5. #25
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    An interesting idea that I'm open to seeing developed, and would consider someday if vetted by trusted LE or .mil organizations, or other SME's. Hard to see why it couldn't be done if a reputable engineer puts their mind to it. As for polymer itself, there's amazing work going on in materials science these days, we're way beyond the era where folks can scornfully dismiss all things made out of 'plastic' as if that is inherently incapable of being tough or reliable. My brother-in-law is a professor of materials science in a large university engineering department, he's always telling me about amazing stuff they're doing with various polymers, ceramics, graphene, and other interesting materials as well as industrial applications. You have to think that at some point, firearms design is also going to reap the benefits of all those super light, super strong materials that have other useful properties as well.

    A related Q I'd ask is what is the primary need driving a polymer receiver. Manufacturing cost savings? Weight savings for the shooter? Improved ease of maintenance? Long-term durability? Or is it mainly driven by marketing and a desire to sell more rifles? None of those options have to be mutually exclusive. But I do wonder if there's an actual real-world need, or if it's mostly a gimmick. Because I don't honestly hear a lot of talk on this forum or any other ones, about the need for a polymer or drastically lighter AR receiver. You do hear about infantry guys saying that the .mil needs to lighten their typical loadouts, obviously this could help there.

    For myself, I don't tend to accumulate many different AR's, I only have two that are setup for defensive/combat use, and one that is more of a range-and-hunting rifle in a boutique caliber (6.5G). For the defensive rifles, there's no way at this point I'd want to be the first-gen adopter for a new unproven polymer receiver design. For defensive use firearms I'm pretty much gonna rely on a proven design.

  6. #26
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    Quote Originally Posted by maximus83 View Post
    A related Q I'd ask is what is the primary need driving a polymer receiver. Manufacturing cost savings? Weight savings for the shooter? Improved ease of maintenance? Long-term durability? Or is it mainly driven by marketing and a desire to sell more rifles? None of those options have to be mutually exclusive. But I do wonder if there's an actual real-world need, or if it's mostly a gimmick. Because I don't honestly hear a lot of talk on this forum or any other ones, about the need for a polymer or drastically lighter AR receiver. You do hear about infantry guys saying that the .mil needs to lighten their typical loadouts, obviously this could help there.
    Frankly, I view most of the plastic 80%'s like EP Armory as the FP45 Liberator of the AR world: cheap and disposable, more for quickly "flooding the zone" and making Grabbers paranoid than anything else. They DO offer the advantage that all you need to complete one is a cordless hand drill (a vise really DOES help), but their only Serious Work use would be in a Red Dawn scenario, ambush a BG, take his weapon and hand the plasticrap off to the next guy.

    OTOH, Grabbertrash particularly hate 'em, so everybody should have at least three just as an F-U to them.
    Last edited by Diamondback; 11-24-20 at 18:39.
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  7. #27
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    The huge appeal of the polymer thing I can see - 3D printing potential. All the other stuff like price, weight are so minor that they don't even matter.
    Although, with that said, 80% Al lowers make even that advantage sort of a wash.

  8. #28
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    Quote Originally Posted by GSPatton View Post
    The huge appeal of the polymer thing I can see - 3D printing potential. All the other stuff like price, weight are so minor that they don't even matter.
    Although, with that said, 80% Al lowers make even that advantage sort of a wash.
    Laser sintering printers might stand a chance of one day producing some pretty formidable polymer gun frames. The main advantage, besides rapid prototyping, would be to produce designs that couldn't be made through injection molding. For example, a one piece monolithic chassis that was the upper, lower, and handguard all in one. Such things would become not only possible but extremely easy.

  9. #29
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    Quote Originally Posted by okie View Post
    Laser sintering printers might stand a chance of one day producing some pretty formidable polymer gun frames. The main advantage, besides rapid prototyping, would be to produce designs that couldn't be made through injection molding. For example, a one piece monolithic chassis that was the upper, lower, and handguard all in one. Such things would become not only possible but extremely easy.
    Are you referring to something like this?:
    https://www.thefirearmblog.com/blog/...eceiver-ar-10/

  10. #30
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    Quote Originally Posted by GSPatton View Post
    Are you referring to something like this?:
    https://www.thefirearmblog.com/blog/...eceiver-ar-10/
    Precisely.

    That's pretty cool. Kind of painful though to see the missed opportunity for a folding stock, where you had two hybrid latch/hinges that would allow the stock to fold to either side. To remove the action parts, you would simply remove the stock by undoing both latches and then slide the BCG out the back. The profile of the combined receivers is begging for that. Especially since you have to have some way of removing the buffer tube anyways. Might as well double as something useful.

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