MPN: LN5-500


  • 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
  • Weight: 0.46 oz.
  • Length: 0.3"
  • Inner Diameter: 0.93"
  • Outer Diameter: 1.05"
  • Shallow Side Depth: 0.06"
  • Deep Side Depth: 0.12"
  • Thread: 1/2"-28


  • .223/5.56 barrel with 1/2"-28 thread pitch

*Barrel outer diameter at the muzzle has to be smaller than 0.75"


Rex Silentium is your go-to manufacturer for quality muzzle devices that you can count on. Doesn’t it make sense to buy the mounting accessories you need for the installation of your brake from them too? When you want a Muzzle Brake Lock Nut, Rex Silentium offers a quality retention nut you can count on.

The Rex Silentium AR-15 Muzzle Lock Nut is a quality lock nut for the application of muzzle devices for the AR-15 platform. Using a lock nut makes timing and installing a muzzle brake much easier than it might be if you had to guess where to put a cone washer. Unlike crush and peel washers Rex Silentium's rifle Muzzle Lock Nuts are reusable and infinitely repositionable. The design of these nuts is such that they protect the threaded barrel area behind the muzzle.

All you need to do to apply your muzzle device using a lock nut is to apply the nut ahead of your device, and screw on the device after it. When the device is applied properly back the lock nut up to it and tighten the two together. The Lock nut and muzzle device will snug up against one another, creating a locking effect holding the muzzle device firmly in place. Some applications may require a bit of liquid thread lock.

The Custom Muzzle Brakes Muzzle Brake Lock Nut is finished in Mil-Spec black to blend into your build flawlessly. Made in the USA by American craftsmen, this hardened steel lock nut is the only retention accessory you’ll ever need.

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Reviews (6)

  • Great idea odd execution

    Posted by D on 18th Jun 2020

    I paired this with a Rex Silentium muzzle brake and loved the initial idea. The place where the execution is odd is sizing of the two devices. Neither one seems to fit any of the wrenches I have in either metric or imperial measurements. I find this to be a lot easier as a timing device than any other crush washer or split washer I've used. Only complaint I can find is the size is weird.

  • lock nut

    Posted by Richard Derrick on 6th Jan 2020

    Solid build, tight lockdown

  • Muzzle Lock Nut

    Posted by Unknown on 9th Sep 2017

    The best locking nut ever no more crush washer love how fit over the barrel

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