Colt M4/AR15 Receiver Extension Castle Nut

(28 reviews)
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Factory Colt receiver extension castle nut for M4/AR15 type rifles.


  • 5
    Colt extension castle nut

    Posted by Bob on 21st Sep 2023

    Great Colt quality. Got it fast .

  • 5
    Barrel nut

    Posted by Poopeye on 23rd Dec 2022

    Worked great , fast shipping.

  • 5
    Keep it Colt

    Posted by John on 2nd Oct 2022

    ArmsUnlimited is my go-to for Colt parts. Working on an M4 clone I needed the Milspec Colt 4 position receiver extension. Armsunlimited was out of stock so I signed up for a notification.. Within days I get a notification in my email that the item was in stock . I ordered it immediately along with a Colt castle nut (had an endplate) and I had it within a few days. All in all, I have used these guys a number of times and it’s always a fair price (no gouging), fast shipping, and all the rest that goes along with great service.

  • 5
    Colt parts

    Posted by Michael Gibbs on 29th Jul 2022

    Colt is good! But once again arms unlimited with their pricing, inventory, and customer service is great!

  • 5

    Posted by Jonathan Dunn on 19th Aug 2021

    Simple and dead-nut dependable.

  • 5
    Great pricing

    Posted by Reuben Oaks on 26th Dec 2020

    Colt quality...

  • 4
    It works

    Posted by Unknown on 6th Dec 2020

    In my experience Colt castle nuts are consistent and work well.

  • 5
    Colt Parts

    Posted by William Mason on 20th Sep 2020

    I prefer Colt parts, AU is a reliable source with good inventory, price, and fast shipping. They already had my business, and have worked to keep it.

  • 5
    Castle nut

    Posted by David G on 1st Sep 2020

    Colt is legit. Great parts to have on standby.