Quantcast

Polymer AR lower catastrophic failure.

Discussion in 'Rifle Country' started by jeeptim, Dec 8, 2018.

  1. jeeptim

    jeeptim Member

    Joined:
    Mar 27, 2010
    Messages:
    644
    Location:
    California
    First off was expecting this and can't believe it took roughly 6500 rounds.
    Was very uneventful.
    I have a 22 conversion that I had in and shoot 200 22rnds swapped back to 5.56 first round it felt wiggly so I pulled it off my shoulder and the buttstock falls to the bench.
    My first thought was ... about time!!
    So swapped a different lower and off to the races.
    Happy it was uneventful.
    It was a cheap 6/7 year old plastic 80% No reason other then it was a
    P.O.S. functioned well for way longer then I ever thought.
    Also had no signs of letting loose.
    So if you gots one expect it.
     

    Attached Files:

    equin, NIGHTLORD40K and chicharrones like this.
  2. beeenbag
    • Contributing Member

    beeenbag Contributing Member

    Joined:
    Feb 10, 2010
    Messages:
    1,324
    Location:
    Grayson, Ky
    Glad you remained intact even after it didn’t.

    I would say at 6500 rounds you got your money’s worth from that lower.

    Safe shooting!
     
  3. WestKentucky

    WestKentucky Member

    Joined:
    Feb 1, 2014
    Messages:
    7,324
    Location:
    Middle Tn
    Classic location. The takedown pin hole really shows as a weak point every time that I see a pic of a failed poly. I'm glad to hear it was quite uneventful.
    Did you find all of the little pieces like detent, detent spring, takedown pin?
    Was there any damage or indication of impact of the bcg on the misaligned parts? Full throttle on gas, or did you have an adjustable block turned down?

    I ask because I have a poly that I am intending to replace, but haven't yet. It seems that they could make a poly with thicker web in this critical area, even if they did so by adding material on the external flats. Would be cheaper and easier than adding a skeleton to the mold before injecting.
     
  4. troy fairweather

    troy fairweather Member

    Joined:
    Mar 21, 2018
    Messages:
    1,898
    yup that's where most fail. put it on a plack as a reminder .
     
  5. jeeptim

    jeeptim Member

    Joined:
    Mar 27, 2010
    Messages:
    644
    Location:
    California
    Yeah like I said uneventful.
    It just kinda felt wobbly that was it.
    No impact nada .
     
  6. Hokie_PhD

    Hokie_PhD Member

    Joined:
    Jan 29, 2017
    Messages:
    2,284
    Location:
    Central Virginia
    I’m glad you’re ok and the only thing was a wobbly receiver.
     
  7. AlexanderA
    • Contributing Member

    AlexanderA Member

    Joined:
    Feb 27, 2011
    Messages:
    4,945
    Location:
    Virginia
    I don't understand why people mess around with polymer lowers when real metal ones are so reasonably priced.
     
    doubleh, Pat Riot, Styx and 2 others like this.
  8. someguy2800

    someguy2800 Member

    Joined:
    Sep 16, 2015
    Messages:
    4,427
    Location:
    Brainerd Minnesota
    My father in law has a bushmaster carbon 15. That one seams reasonably reinforced. The only one I would buy personally is the gwacs one.
     
    KansasSasquatch and boom boom like this.
  9. boom boom
    • Contributing Member

    boom boom Contributing Member

    Joined:
    Sep 24, 2007
    Messages:
    2,674
    Location:
    GA
    Key word is 80% and very little paper trail. Polymer is easier to work with than Aluminum for a lot of people. Otherwise, they are a bit cheaper and lighter. One polymer lower is literally poured into molds and requires little if no filing afterwards. As the post above notes, it is strong enough to last thousands of rounds. Easy peasy.

    Second, a lot of folks have familiarity with polymer now due to Glocks, etc. The polymer Glock 80% knockoffs have me even thinking about building one as a lark. T

    Expect the anti-gunners to start cracking down on "ghost guns" as their latest crusade which will be self defeating as nothing so much makes someone want to buy something as forbidden fruit.
     
    Skylerbone likes this.
  10. jmorris

    jmorris Member

    Joined:
    Sep 30, 2005
    Messages:
    11,873
    I have a couple of Cav plastic lowers one that I even beat up with 458 socom for awhile. They don’t use a thread in buffer tube or separate grip though so are not as fragile in the area where yours broke.

    2BC784D6-05BE-42F3-A11F-D038874C7378.jpeg
     
  11. KansasSasquatch

    KansasSasquatch Member

    Joined:
    Jul 22, 2012
    Messages:
    1,941
    Location:
    LV county KS
    The Carbon 15 isn't exactly a great rifle but I trust them a lot more than I would trust one of the 80% polymer lowers. I don't know about the 80%'ers but I do believe the Carbon 15 is fiber reinforced, which should be less prone to breaking. My dad used to have one and between the 2 of us I'd estimate it easily had 5-6k rounds through it without any issues. It seemed to like the BCG to be dripping wet if we wanted to put more than 3 mags through it in a range session, but CLP is cheap enough.
     
  12. someguy2800

    someguy2800 Member

    Joined:
    Sep 16, 2015
    Messages:
    4,427
    Location:
    Brainerd Minnesota
    Pure nylon is very soft and flexible, like a cool whip tub, so all of the polymer lowers and polymer pistols are going to have a high percentage of filler to get the flexural modules to where it needs to be, either chopped carbon, glass, or both. Probably like 40% of the material is actually filler. I believe the bushmaster ones are carbon filled, hence the name. It’s alot lighter than glass filled and let’s the manufacture claim its “carbon fiber polymer”.

    I work in the plastics industry and the things you can do with the right polymers and good design for manufacturing are impressive. A Glock is a better polymer pistol than if you tried to make it out of aluminum because it was designed with polymer in mind, but you can’t take a design that was meant to be metal, like an AR15 or 1911 and just directly reproduce it in polymer without redesigning it first.
     
  13. Elkins45

    Elkins45 Member

    Joined:
    Dec 25, 2009
    Messages:
    4,460
    Location:
    Northern KY
    I bought one of those when they were on sale for $89. I wish I had bought a dozen. I put a 16” pencil barrel upper on it and it has become easily my favorite rifle.
     
    chicharrones likes this.
  14. chicharrones

    chicharrones needs more ammo

    Joined:
    Jan 19, 2010
    Messages:
    6,191
    Location:
    Galveston Bay is an Hour Away ©
    The Cav/GWACS poly lower has more material in that area, too.

    more-meat.jpg
     
  15. Storm1969

    Storm1969 Member

    Joined:
    Dec 1, 2018
    Messages:
    28
    I am inches away from getting a couple 80% polymer lowers. would they hold up to 6 grendel or 6.8?
     
  16. Deerhunter357

    Deerhunter357 Member

    Joined:
    Mar 26, 2018
    Messages:
    1
    I don't have any experience with these polymer lowers but I do have a Windham weapon Carbon Fiber Ar and it was designed with significantly more material in critical areas compared to my aluminum lowers . Does anyone here have experience with Windham's offering when it comes to durability ? It feels and looks like quality .
     
  17. bfoosh006

    bfoosh006 Member

    Joined:
    Jan 29, 2008
    Messages:
    627
    I own one of the Bushmaster Carbon 15"s ( R97S ? ) ... super LtWt... but sadly not anywhere near as strong as an 7075 lower.

    And I am just going to throw this out there... what are the odds the OP's could be glued back together>

    I realize it would be easier to just buy a 7075 lower... but for the sake of argument ?
     
  18. someguy2800

    someguy2800 Member

    Joined:
    Sep 16, 2015
    Messages:
    4,427
    Location:
    Brainerd Minnesota
    Plastic is not very accepting of glues and epoxies. It will never be as strong as it was before, which was apparently inadequate to begin with.
     
  19. Enfielder

    Enfielder Member

    Joined:
    Nov 15, 2010
    Messages:
    106
    Location:
    Finger Lakes, Ny
    Gun buyback $$$$!!!!
     
  20. illinoisburt

    illinoisburt Member

    Joined:
    Jan 30, 2014
    Messages:
    680
    Location:
    Central Alabama -- recently relocated from Chicago
    By chance do you have a pic of the inside of the receiver? It seems many of the poly failures with similar location have been the 80%'s. Not sure if its a milling/heating/stress issue or sidewalls cut down too thin, or possibly they are made with different polymers than complete factory lowers?
     
  21. GunnyUSMC

    GunnyUSMC Member

    Joined:
    Jan 3, 2012
    Messages:
    4,049
    Location:
    Denham Springs LA
  22. Barr

    Barr Member

    Joined:
    Apr 7, 2006
    Messages:
    485
    Location:
    Upstate SC
    Aluminum budget lowers such as Andersons and PSAs go for $30-50 on sale. There is merit in the comment that polymer is easier to cut at home. Still for longevity, good anodized aluminum has it in spades over polymer.
     
    badkarmamib likes this.
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice