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Magpul Enters the AR Stabilizing Pistol Brace Market with its BTR and BSL Braces

As part of it's #SHOT2020 launches, Magpul is bringing a couple of AR pistol stabilizing braces to market this year. The BSL, above, left, and BTR, above, right, might look like their beefier, rifle stock brethren when viewed from the side, but in profile, the braces are much thinner and are designed only to provide stability when firing one-handed, with an extended arm.

The braces slip onto mil-spec carbine receiver tubes, offer length-of-pull adjustments for different forearm lengths using a pinch-operated catch, and have a QD cup where a shoulder pad would be. With a shortened, one-point sling attached this way, it applies tension on the pistol when held by an outstretched, single arm. Magpul says the brace works fine without a sling, but it definitely adds a lot more stability. The height of the rear sling mount accommodates a heads-up firing stance and is positioned to provide a sightline for rail-mounted red dots.

As far as we can tell, a stabilizing brace alone doesn't make an AR pistol. Talking with industry folks regarding the ATF's guidance on the subject leads us to think intent plays a large role in determining whether a firearm is an SBR or a pistol. In this case, the design of Magpul's braces (that include a sling attachment on the trailing end) more-or-less suggests strongly that the firearm isn't meant to be shouldered. But, using a magnified optic with three or four inches of eye relief on a firearm equipped with a stabilizing brace suggests the intended use of the firearm not as a pistol, but as an SBR.

Practically speaking, this means the ATF might argue in court that it doesn't matter what parts are used to make the gun, or even if it can be shouldered, but if the combination of parts mean the firearm can only be fired from the shouldered position, it's an SBR. The math looks like this: pistol stabilizing brace + rifle optic = likely SBR. We say likely, because, hey, it's the ATF and nothing is black and white.

We asked Magpul for some clarification on the legalities of pistol configurations and they pointed us to a FAQ they've written, and that we've included below.

Magpul BSL Pistol Brace

Magpul BSL MAG1143 

  • Designed and intended for use as a stabilizing accessory for one-handed firing
  • Tool-less, one-handed adjustment
  • Ambidextrous rear QD cup allows sling tension to be applied while firing with one hand to improve stability
  • Compatible with mil-spec carbine receiver extensions
  • High-strength polymer and metal construction
  • M-LOK compatible slot for additional sling mounting options
  • Color: Black
  • MSRP: $60

Magpul BTR Pistol Stabilizing Brace

Magpul BTR MAG1079 

  • Designed and intended for use as a stabilizing accessory for one-handed firing
  • Tool-less, one-handed adjustment
  • Ambidextrous rear QD cup allows sling tension to be applied while firing with one hand to improve stability
  • Compatible with Mil-Spec carbine receiver extensions
  • High-strength polymer and metal constructions
  • M-LOK compatible slot for additional sling mounting options
  • Color: Black
  • MSRP: $60

COMPATIBILITY

Magpul states that both the BSL and BTR are compatible with Mil-spec carbine receiver extension equipped AR Pistols. Not compatible with proprietary, pistol, or commercial receiver extensions. All ATF, NFA, state and local rules and laws apply, where applicable.

ATF has ruled that attaching stabilizing braces with certain features will not make a firearm NFA controlled. This product conforms to this ATF precedent. As of December 10, 2019, ATF is no longer issuing classification letters for firearm accessories, including stabilizing braces.

These products are designed and intended to serve only as a forearm brace for one-handed firing of a pistol.  They are not intended to be fired from the shoulder. Any redesign or reconfiguration of these products may render the attached firearm NFA controlled. The user is exclusively responsible for determining the correct application of state and federal law based on the unique configuration of each firearm.

Magpul's BTR/BSL FAQ:

Is there an ATF opinion letter for the Magpul BTR and BSL?
A: The ATF is no longer issuing classification letters for firearm accessories, including braces. The ATF has seen these products, and they have been specifically designed to closely conform to the features and limitations identified in existing opinion letters. An additional data point is that many common brace-type products do not have an individual letter for that specific product and instead rely on referring to classification of previous products in a manufacturer’s line, and this is really no different. In fact, we conform quite closely to approved features, function, and dimensions in the body of existing classifications. It is still the responsibility of the customer to ensure that their specific configuration is compliant in their location.

Q: Is the BTR/BSL a stock?

A: No. The BTR and BSL are expressly designed to aid single handed operation of AR-based firearms. The features, dimensions, and characteristics have all been chosen specifically for this function.

Q: Can I fire this from the shoulder?

A: The BTR and BSL are designed to aid single handed firing of AR-based firearms. Any other use is outside the intended purpose of the product. There are several ATF opinion letters regarding the shouldering of brace-equipped firearms, and we encourage reading those opinions to be best informed about current interpretations.

Q: Can I use this on an A5 extension?

A: The BTR and BSL are specifically designed for a standard, mil-spec carbine-style receiver extension*. Using an A5 or other extension that is longer than a regular carbine extension will allow the BTR and BSL to extend to a length that exceeds the ATF opinion limitations on extended length of 13.5”. If the BTR/BSL are used on an A5 length extension, permanent modification is required to ensure maximum length is not exceeded

Q: Can I use this in conjunction with a LAW Folding Stock adapter or a similar product?

A: The BTR and BSL are specifically designed for standard, mil-spec carbine-style receiver extensions* without any additional accessories that increase the effective length of the receiver extension. Adding any accessory or component that results in the carbine receiver extension protruding further to the rear may allow the BTR and BSL to extend to a length that exceeds the ATF opinion limitations on extended length of 13.5”. If the BTR/BSL are used with any of these accessories, permanent modification is required to ensure maximum length is not exceeded.

Q: Doesn’t a standard carbine receiver extension turn a firearm into a rifle?

A: No. The ATF has issued several opinions that state that a carbine receiver extension does not in and of itself make an AR receiver into a rifle, and at least one brace classification letter has been issued approving the use of a carbine receiver extension with a blade-style brace and maintaining pistol classification. **Final configuration is what is evaluated by the ATF, and it is recommended that the user be familiar with all federal, state, and local laws and regulations to make sure that their final configuration is compliant.

Q: Do I need to use a sling with the BTR/BSL?

A: It is not necessary. The shape of the BTR/BSL provide stability simply by contacting the forearm. By using a sling, however, additional tension can be applied to add stability and control. The rear-mounted QD socket provides a centered sling mounting point for this purpose and can be used with either hand. A QD sling mount can also be added to the M-LOK slot on either side of the BTR or BSL, which can add some additional tension into the user’s forearm, but then is optimized for firing from a specific (left or right) hand.


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