Tactical Handyman: How to Fix a Stretched SB15 Brace

The SB15 Brace has changed what we expect from AR pistols. It fits most standard pistol buffer tubes and several are now being made specifically for the SB15. The problem is that there is no standard outside diameter for AR pistol receiver extensions (buffer tubes). Some, like those from KAK Industries are very slim. There are some that are quite thick like those from Spike’s Tactical. Others are somewhere in the middle like the new tube from EXOS Defense.

The tight fit that results from using a thicker tube is great until you try to change to a new tube that is slimmer than your current tube. You will quickly find that your SB15 Brace is stretched to the point that it spins freely on the buffer tube and, in extreme cases, it can even slide right off. This renders the SB15 effectively useless.

This is the position that the Tactical Handyman recently found himself in. He had an SB15 on a Spike’s Tactical Pistol Buffer and found that it was stretched to the point that it would nearly fall off under its own weight on the new EXOS Defense pistol buffer tube which has a perfect outside diameter for use with the SB15. Here is how he fixed it…
AR Pistol JTT IG 1

You will need the following:

  • Stretched out SB15 Brace
  • Soup/Stock Pot – Note: This pot needs to be big enough to hold the SB15 and enough water to cover it. Preferably, it should be large enough that it has room to hold all of that and little more so it doesn’t boil over.
  • Water
  • Stove
  • Timer
  • Kitchen tongs


This is super easy if you can boil water which might not be all that easy for some of you. If you haven’t figured it out by now, we are going to boil your SB15. Heating the rubber will cause it to shrink back to its original shape. In fact, in my case it almost seemed a bit tighter than it was originally.

  1. Remove the SB15 from your AR pistol. Note: If you boil your AR pistol, you deserve anything bad that happens to you.
  2. Drop your SB15 into a still cool stock pot. Note: Seriously, don’t heat the pot first. I shouldn’t even have to write this but I know there is some guy out there who already has the water boiling and is getting ready to burn his face off.
  3. Pour enough water into the still cool stock pot to completely cover the SB15 (it will sink) and not so much that the pot is in danger of boiling over.
  4. Remove the SB15 from the stock pot (leave the water).
  5. Bring the stock pot with water to a rolling boil. Note: You will probably want to set the burner as high as it will go to speed the process. Turn it up to 11.
  6. Lower the burner to about medium heat or just enough to keep the water boiling.
  7. Place your SB15 into the boiling water. Note: Do this carefully. Your skin is probably allergic to boiling water.
  8. Set your timer for 10 minutes.
  9. Turn off the burner when 10 minutes elapses.
  10. Remove the SB15 from the pot with your tongs and set it somewhere to dry and cool. Note: You can do this immediately after turning off the burner. Be careful because you have delicate little girl hands and the water is literally boiling. Drying will not take long since most of the water on the brace will evaporate immediately.
  11. Test fit the brace on your buffer tube only after it cools to room temperature. Note: I was able to speed the process by putting the brace in the refrigerator for the last few minutes of cooling. This is kind of like a refreshing cool towel after the steam towel at a barber shop.
  12. Repeat the process if necessary.

AR Pistol JTT IG 2

Wrap Up

In my case, I was able to take an SB15 that was basically falling off and return it to like new condition or maybe even a bit better in terms of fit. It will even stay in place on the KAK tubes which are some of the slimmest I know. Don’t scrap that stretched out SB15! Try boiling it first.

3 Responses to Tactical Handyman: How to Fix a Stretched SB15 Brace

  1. Max October 15, 2014 at 18:46 #

    Haha, nice. Honestly, whenever I visit your blog I immediately wonder why nobody seems to comment much. Maybe you aren’t controversial enough?…

  2. Z October 15, 2014 at 21:11 #

    Haha, 11!

  3. jurmond October 16, 2014 at 03:21 #

    I don’t have a SB-15 yet, but my tube from KAK has a diameter of 1.2 inches, which is the upper limit of the SB-15’s official size rating. Anything bigger would be a stretch.

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