SB Tactial SBA4 Brace: Bringing Adjustability to the Fixed

Released at SHOT Show in 2019, the SBA4 is one of the newer AR pistol braces offered by SB Tactical, and among many along its AR, AK, and shotgun models. Highlight features to the brace include an adjustable length, a wider polymer body for increased support, and a QD mounting point that all provide improved comfort and function for shooters.

The SBA4 is intended as a follow-on to its predecessor, the SBM4, with the A4 having a more rigid forearm support sides, and a 1” hook-and-loop strap to secure the brace to the arm. However, where the A4 differs is the newer brace now accepts any 7075 mil-spec carbine buffer tube (included with brace) and thus has a 5-position adjustable length.

The older SBM4 only accepted pistol buffer tubes and was not adjustable. And unlike the older SBM4, the newer A4 brace now also includes a metal ambidextrous QD mounting point for slings forward of the buffer adjustment pin.

Fully collapsed, the A4 has a minimal length of 7.5”, while on a fully extended carbine buffer tube measures 10.25”. Understanding these measurements can become impetrative when determining the overall length of an AR build to meet ATF regulations on AR pistols.

With its wider angled polymer body, the A4 also enables an improved cheek weld for the user. This is an improvement over the SBM4, and for comparison an improvement over the smaller, thinner, and lighter Magpul CTR buttstock.

The SBA4 is available in Black, OD Green, FDE, or Stealth Grey.

Product Evaluation Scores:

  • CostAverage (3/5): At an MSRP of $169.99, the SBA4 is also available at secondary sites for approximately $129, with some retailer coupons or sales during holiday’s providing the brace for even a lower cost. Given that SB Tactical is the market leader for firearm braces, there is no direct competitor for comparison to the A4. However, its predecessor the SBM4 ($99) with a similar design, does include many of the same stabilization aspects, but the SBM4 is only for use with pistol buffer tubes and as such is not adjustable. Even the more recent SBA3 ($169) is lighter and adjustable, while the SBPDW ($299) is one of the heaviest AR pistol braces on the market. In all this gives the A4 an average price range for its time on the market and amount of materials involved.
  • Comfort Good (4/5): For its comfort factor, the sides of the A4 were very rigid and gave support to the forearm rather well. This prevented the AR pistol from canting, while the support strap kept the overall brace secured despite the weight of the firearm held out at full extension to the body. Indeed, users with thicker forearms may find it more difficult to get a deeper position within the brace at first, until the rubber has had time to adequately break in. The nylon support strap was slightly elastic which made getting a positive/tight bond somewhat difficult, but not unattainable. One notable improvement for the A4 was the wider 2.8” angled polymer body that gave the user more surface for a positive cheek weld. This was an improvement over the SBM4’s width of 2.0” and thus narrower angle/less surface for contact. Internet research showed a number of aftermarket replacement straps to most SB Tactical braces, including the A4 and the recommendation to the manufacturer would perhaps examine improving or offering alternate straps for improved comfort and function.
  • Durability – Good (4/5): The SBA4 was made with dominantly a polymer body; which gave it a similar profile to a A2-style stock but with more rigidity than the SBA3 brace, and provided a stable platform for a positive cheek weld. The forearm support sides were made from a rubberized ABS material that gave the sides sufficient flex to contour around the arm. Over time and use the SBA4’s support sides did not collapse nor overlap, a problem that was a common concern for the SBA3, and rather the A4’s sides were molded to form and maintain a wedge shape when not in use, rather than loop. It is most likely that over time, the element of the A4 that will wear out first will be the hook-and-loop material to the 1” support strap (another reason there are aftermarket straps available).
  • Functionality Average (3/5): From a functional aspect the SBA4 was a little tricky to don on the forearm, it being necessary to fully loosen the support strap and push the arm through the sides. This was the same process similar to securing the older SBM4. The newer A4 also had more rigidity in its forearm support sides. These defiantly improved support to the AR pistol given its wide, angled dimensions that contoured around the arm once the support strap was tightened. Adjusting the position on the carbine buffer was a little tight, most likely attributed to variances in buffer tube dimensions and that not all tubes are a one-size-fits-all. But with a little effort the A4 was able to move across all five (of six) positions on the carbine buffer tube. The ambidextrous QD mounting points were full metal and accommodated a variety of mounting accessories. The feel of the QD point (forward of the adjustment pin and closer to the receiver) gave the overall AR pistol a tighter feel on the sling, and was a little distracting when raising the brace up to the cheek as it put the hardware right there by your face. Some adjustment of your sling may be necessary to accommodate this QD location.
  • Weight Fair (2/5): Weighing in at just 10 ounces (without buffer tube) the SBA4 is relatively lightweight, and among the line of other SB Tactical braces had a fair scoring. As noted above, once secured to the arm, the brace balanced the AR pistol and helped alleviate the weight of the firearm forward of the body. In comparison, the heaviest AR pistol brace in the SB line is the SBPDW (18.14 ounces) while others, such as the SBM47 (15.5 ounces), SBM4 (8.7 ounces), and SBA3 (6.75 ounces) demonstrate the weight of the SBA4 is towards the heavier side given most other AR pistol braces trend to a more minimalist approach with less materials that achieve the same results. The added weight is the payoff for the SBA4 to have that five-position adjustability.

Overall Rating – Average (16/25)

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***Editor’s Note: The history and ruling of AR/AK pistol braces is a sordid one. From the initial ATF ruling in 2014, the “clarification” letter by Max Kingery (then-acting Chief of Firearms Technology Criminal Branch) in 2015, and a second ATF ruling in 2017, and the most recent ATF clarification in 2019 the regulation agency has struggled to provide a clear ruling on the application of such devices. Specifically shouldering, the topic of proper use of braces has caused more internet arguments among “internet lawyers”. Currently ATF guidance as of 2019 states as follows:

“To the extent the January 2015 Open Letter implied or has been construed to hold that incidental, sporadic, or situational ‘use’ of an arm-brace (in its original approved configuration) equipped firearm from a firing position at or near the shoulder was sufficient to constitute a ‘redesign,’ such interpretations are incorrect and not consistent with ATF’s interpretation of the statute or the manner in which it has historically been enforced.”

As such, Per the ATF the use of an AR/AK pistol brace comes down to intent. Thus, accidental or “sporadic” shouldering of an AR pistol brace is not illegal. When consistently shouldered however, it demonstrates the intent to subvert regulations on SBRs by utilizing the AR pistol and brace as an impromptu work-around (and thus illegal). The same is said by adding accessories intended for precise accuracy as found with an SBR, such as scopes or utilizing irons. During the course of evaluations, any shouldering of the SBA4 was purely accidental, as efforts are made to test the brace within various range iterations to the extent of design, while still adhering to ATF regulations.


I am reviewing this product as a courtesy to the manufacturer and via STL Shooting Enthusiasts, so that I can evaluate it and provide my honest feedback. I am not bound by any written, verbal, or implied contract to give positive reviews. All views are my own, and based off my personal experience with the product.

The views and opinions expressed on this website are solely those of the author. The views and opinions do not necessarily represent those of the administrative staff, and/or any/all contributors to this site.