Tag Archives: Brace

Assembling an AR Lower – Step 9 of 11: Installing the Buffer Tube and Arm Brace

There are three types of buffer tubes for ARs and the one you pick depends on what you are building.  There is the traditional long A2 fixed stock style buffer tube, the 6 position M4-style telescoping stock tube and lastly the pistol buffer tube. Since I am building a pistol, that will be our focus.  The pistol buffer tube has no provision for a stock and is just a straight tube.  Do not use a rifle tube on a pistol build just to be safe legally.  Other than that, the installation is almost identical other than the backplate (shown below the buffer tube in the next photo) which is indexed for rifles but typically not for pistols.

Step one:  Install the rear takedown pin assembly.  Insert the pin from the right to left.  Put a dab of Tetra Gun Grease in the detent hole and then push the pin and spring in.  The grease will help retain it.

Step two:  Put the backplate on the tube and thread it into the receiver almost to the end.  Watch the detent spring and make sure it is compressing properly into the hole and not bending.  On pistol builds I will push the plate down with one hand while threading the buffer tube on with the other.  Stop in time to insert the buffer spring and detent in their hole.  Push them down and thread the buffer tube on the rest of the way.  Note, you can stake the tube into position or use a small dab of blue Loc-Tite to hold the buffer tube in position.  Note how the front of the tube overlaps the detent pin just enough to hold it in position.

Step three:  Install the Arm Brace.  The SB Brace I got from Palmetto has a hollow rubber cylindrical hole for the buffer tube to go down.  Of course that thing will not want to slide down the tube by itself.  I lightly lubricate the buffer tube with silicone spray and then slide/hit the brace into place.  Only turn the brace clockwise as you install it lest you unscrew the buffer tube.  I did use a rubber mallet to help get it down the tube faster.1

So with that the brace is installed.  My next post will be about attaching the upper and finishing the assembly.


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The actual March 2017 ATF letter approving stabilizing braces has a section about customization you need to know about

Yes, I am late to the game on actually reading the March 2017 ATF letter clarifying the use of stabilizing braces.   It’s been on my to-do list for some time and I finally did.   I do think this is very helpful – notably:

With respect to stabilizing braces, ATF has concluded that attaching the brace to a handgun as a forearm brace does not “make” a short-barreled rifle because in the configuration as submitted to and approved by FATD, it is not intended to be and cannot comfortably be fired from the shoulder.

With that said, folks need to bear in mind  the very next paragraph:

If, however, the shooter/possessor takes affirmative steps to configure the device for use as a shoulder-stock – for example, configuring the brace so as to permanently affix it to the end of a buffer tube (thereby creating a length that has no other purpose that to facilitate its use as a stock), removing the arm-strap, or otherwise undermining its ability to be used as a brace – and then in fact shoots the firearm from the shoulder using the accessory as a stock, that person has objectively “redesigned” the firearm for purposes of the NFA.

So what this means is if you put a brace on a pistol, use it as-is.  Do not remove the Velcro straps, stick foam in the brace to make it solid, and/or attach the brace in such a way that it is permanently so long that it could not connect to the forearm.

I always recommend that people read guidance directly for themselves.  Here is a link to a PDF copy of the letter so you can do so: Reversal of Stabilizing Braces – ATF-letter – March 2017 — please note I changed the file name when I saved it but the content is all original.

All in all, I think this is a much needed clarification overall.  Just bear the customization clause in mind when you are building, or modifying, your weapons.

Yes, for the record, I do not like the fact that short-barreled rifles or shotguns need special regulation per the NFA but the braces do provide an option for folks. Also, please note that I am not a lawyer and this should not be construed as legal advice.


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