JMAC Customs ST-6 Skeletonized Buffer Tube – Review

What is the JMAC ST-6 Skeletonized Tube? It’s a custom machined skeletonized replacement buffer tube for guns that don’t use a buffer in the stock. It fits most stocks and braces that work with a normal AR-15 buffer tube. It has six length of pull settings just a like a normal buffer.

I had a SIG MCX pistol with a folding brace that I hated. I wanted to run a SBA3 pistol brace. This ST-6 Skeletonized buffer makes that work. The JMAC ST-6 attaches directly to the SIG folding mechanism. JMAC also sells other adapters that will fit different platforms like an AK.

What I started with.

Couldn’t you just use a regular buffer tube? Sort of. This attaches directly to the SIG folding mechanism that came with my MCX pistol so that no other adapter is needed. Also, it’s lightweight, well made, and looks amazing.

JMAC is currently out of stock but is expected to a get a new shippment in November 27. You can preorder on their website now.

Remember it’s illegal to put a stock on a pistol and we shouldn’t be shouldering pistol braces. If you are using this for a rifle or an SBR, I can say that this would provide a much better cheek weld for optics than what comes on the SIG MCX Virtus pistol or rifle.

The ST-6 has a snug fit with the SBA3 brace with no play or slop. I’m pleased with both the look and function of the JMAC ST-6 and think it’s a great upgrade.

Weight: 0.194 lbs (I weighed it)

MSRP: $114

*Installation note. The SBA3 will fold and lock as long as it’s set to the longest length of pull. If you want it to lock in a shorter configuration then you would need to remove a small amount of material from the SBA3. This has nothing to do with the JMAC ST-6 but is more about the width of the SBA3.

About the author: True Pearce is the Managing Editor at GunsAmerica. He’s a competitive shooter, hunter, instructor & attorney. You can see and follow his adventures on Instagram. @true1911

{ 4 comments… add one }
  • Slim November 27, 2020, 8:46 am

    Can someone please tell me how this will work on an AR that requires the true buffer tube so that the spring and buffer can take up the bolts need for rearward and forward movements in order to cycle the weapon? Didn’t want to filter through the entire thing when saw the part and knew right off the bat its not going to work for 99.9% off all AR’s made unless they are FN type rifles that use a different setup.

    • Tom Cruise November 27, 2020, 8:11 pm

      Literally says it only works on non-buffer firearms

  • WADE November 23, 2020, 10:23 am


  • GIUSEPPE Mantia November 23, 2020, 4:03 am

    I can’t wake for it.

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