ET Arms PlumCrazy Gen II Complete AR-15 Lower Receiver w/ M4 Buttstock

ET Arms

MSRP: $149.99
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The ET Arms PlumCrazy Gen II Complete Lower Receiver w/ M4 Buttstock is engineered for the acceptance of mil-spec components and works on any AR-15 upper receiver!

Milled from a proprietary variant of glass-filled nylon-6, the PlumCrazy multi-cal lower receiver is more resilient to damage than traditional aluminum lowers. Durable & lightweight — with exceptional structural integrity and excellent chemical resistance — these ET GEN II receivers have been proven on training ranges with round counts of 50-97k cycled through with no issues.

The ET Arms PlumCrazy GEN II AR-15 complete multi-caliber lower receiver — continues to exceed expectations and redefine the standards for what an AR polymer lower receiver can be. 


  • Milled from premium, glass-filled nylon-6 polymer
  • Winter/over-sized trigger guard
  • Improved ergonomic grip w/ trap door
  • Polymer buffer tube with 6-position collapsible/adjustable stock
  • Fire controls require no lubrication
  • Castle nut has been factory torqued and staked
  • Lighter & stronger than aluminum — can be run over at the mag well without being crushed
  • Retains color when scratched — scratches can be removed with WD-40 and a green scratch pad
  • New to Gen II: Reinforced water line and internal pocket radius toward the rear of the trigger, which eliminates a previous issue with the backstrap breaking


Please Note: Manufacturers warranty will be void if:

  • The seal is broken — DO NOT tighten the castle nut — The castle nut is factory torqued with a special plastic indicator seal in it.
  • Installed on a pistol upper — Lower CANNOT be used to build an AR pistol.


3 Reviews Hide Reviews Show Reviews

  • 4
    Great product

    Posted by Walter thomas on May 14th 2024

    Great product

  • 5
    Et arms lower

    Posted by william myers on Dec 25th 2023

    This is my 4th. They are well worth the money. I say that as a casual shooter. So I rate them high. Don’t know what 100000 rds would be like but for me they are great

  • 3
    Loose Castle Nut

    Posted by Daniel R. on Oct 4th 2020

    I have yet to fire this build. Upon receiving my upper and finishing the build I noticed that the castle nut can twist left to right almost an 1/8" inch. I will contact manufacturer for return/repair info. ***Keep in mind the buffer tube is not to be tampered with as stated in notes at the bottom of description. I have done nothing to the buffer tube. I will add an additional review with results later.