Threading a PKM Barrel

We thread a LOT of barrels.  Most of the rifles we build end up with threaded muzzles either for a brake or a suppressor.  We even thread some “hard to do” projects like little Beretta 21A barrels.  But when a friend called us to ask about threading a PKM barrel, we thought it would be a cool project with a few challenges.  So, we were excited!  

Here is the finished result.  Now, let’s talk a little about the challenges and the elegant solutions our master machinist Jason Nixon came up with.

The first concern was a proper shoulder for the new muzzle device.  Our friend wants to run a Rugged Suppressor’s Radiant762 on this belt-fed machine gun.

The front sight base is attached to the barrel and would need to provide the shoulder.  Which meant we needed to “true” that forward surface.

The original muzzle device on this barrel is a flash hider that is attached via left-handed metric threads.  A spring-loaded detent pin in the top of the front sight base engages a notch on the flash hider to keep the device in place.  Notice the detents on the back of the flash hider and the pin on top sitting in a notch.

Here is a picture of the flash hider removed, the detent pin and spring removed and you can see the last little bit of factory left-handed metric threads.  The customer needed 5/8×24 threads for his new suppressor muzzle brake.  

So, after taking a few cleaning/truing passes on the front sight base (you can barely see some shinny cut marks around the detent hole), the muzzle got a new 5/8×24 thread, perfectly concentric to the bore.  We then made a small relief cut behind the new threads.  You see, the factory tenon length was longer than we needed for the 5/8×24 tenon length.  So, here is where things get more interesting…

Instead of cutting the end of the barrel back slightly, we could retain enough original metric threads to allow the original factory flash hider to be used.  All we needed to do was fabricate a spacer that would sit over the metric threads and provide the shoulder for the new muzzle brake.

Here is the barrel now with the spacer and Rugged muzzle brake installed.

PKM barrels are NOT cheap and aren’t always easy to find.  We were able to retain use of the original factory flash hider but also provide the ability to now install one of the best suppressors on the market making this already super cool belt-fed machine gun even cooler (and quieter too!)