Carbine Buffer Tube / Receiver Extension

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First Generation Buffer Tube (Receiver Extension) for Colt sliding stock models: XM177, XM177E2 and Colt Commando Models up to the 1980's.

Original Colt variants were first 2 position - just like this one.

In the 80's it was replaced by the 4 position

Most current builds now use a 6 position


  • 2 Position Mil-Spec size (Made in USA)
  • 4 Position Mil-Spec size (Genuine NOS Part) (Made in USA)
  • 4 position Commercial Size (Made in USA)
  • 5 Position Mil-Spec (Made in USA)
  • 6 Position Mil-Spec Size (unknown origin)
  • 5
    Perfect Replacement for Old Commercial Extension

    Posted by JCFlag on 14th Jul 2019

    My Frankford Arsenal machinegun had a commercial diameter buffer tube that was too long (allowed BCG gas key to strike lower receiver under recoil) and the stock adjustment holes were worn out. I ordered the 4 position commercial tube from RetroRifles. It fit perfectly inside the fiberlite stock and threaded easily into the receiver. The length is correct so the gas key cannot strike the receiver. Best part, the back end is straight up and down, not canted like other commercial diameter buffer tubes. Thanks RetroRifles.

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