MPN: LN2-625


  • Align muzzle devices at ease with no special tool
  • Protects muzzle and threads
  • Reusable
  • Updated version allows for bull barrels up to 0.930" in diameter and 2 different depths for muzzle concealment options
  • Made in USA


  • Material: Hardened steel
  • Finish: Mil-Spec Black Finish
  • Weight: 0.39 oz.
  • Length: 0.3"
  • Inner Diameter: 0.93"
  • Outer Diameter: 1.05"
  • Shallow Side Depth: 0.06"
  • Deep Side Depth: 0.12"
  • Thread: 5/8"-24


  • .308/300 Blackout barrel with 5/8"-24 thread pitch


  • 1x Rex Silentium .30 Cal Muzzle Lock Nut

Barrel and Muzzle Device Sold Separately


Buying something as seemingly insignificant as a.30 Cal Muzzle Lock Nut ought to be no big deal, but if you want to build the best custom system, why would you leave anything to chance. A muzzle lock nut protects the threads on your muzzle while you work on your rifle. It makes timing your muzzle devices easier than working with other retention devices. Why would you bet those final details on just any piece when you can choose a .30 Cal Muzzle Lock Nut from the specialists at Rex Silentium?

Rex Silentium Muzzle Lock Nuts allow the armorer to install muzzle devices without special tools, crush or peel washers. They’re made in America from U.S. Steel that’s hardened for durability. You can use the .30 Cal Lock Nut over and over again without concerns about loss of stability. They’re finished with a durable black Mil-Spec coating that will blend in with your build and hold up against all the changes and adjustments you might need to make, even if you’re a habitual gas tuner and like to try different muzzle brakes routinely.

Even if you’re not using a muzzle device, the .30 Cal Muzzle Lock Nut is a great way to protect the threads on the end of your barrel so that you keep your options open to use a muzzle device down the line. Clean protected threads are far easier to work with than flattened threads full of grime any day.

The updated version now allows for bull barrels up to 0.93" in diameter and provide two different depths for muzzle concealment options. For Rex Silentium brakes that use thread adapter, the deep side of the updated lock nut will completely conceal the adapter.

The Rex Silentium .30 Cal Muzzle Lock Nut is an easy choice and a smart one too.

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Reviews (6)

  • Muzzle lock nut

    Posted by Kevin on 3rd May 2020

    Fits good a lot bigger then I thought it would be about the size of a quarter

  • Clean setup

    Posted by George on 6th Oct 2019

    I had no idea these existed. I saw this jam nut on a custom 300 blkout I ordered and now its what I am using on my current build in progress. It does two things, one it makes timing a muzzle device super easy, and two, by using the Rex Silentium Muzzle Lock Nut there is no stress on the barrel as with using conventional crush washers. I recommend this product.

  • Superb product!! Excellent fit, finish, and function.

    Posted by Tom on 2nd Apr 2019

    Highest quality product that was obviously designed to function perfectly when aligning any muzzle device. Threaded portion is actually thin, as the conical shape is recessed for the barrel.

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