Legal Battle Still Rages Between SIG Sauer and ATF

SIG Sauer’s forthcoming MPX was one of the biggest hits at SHOT Show last January. Set to be released in several different configurations, the pistol caliber carbine (or SMG for LE/Military) looks poised to capture the upper end of this niche market. Unfortunately, the rifle’s release has been met with stiff resistance from the ATF. One version of the MPX in particular has been the catalyst for this controversy. The standard version of the carbine (dubbed MPX-C, photo below) sports a 16” barrel in order to comply with NFA requirements. Because a welded muzzle device can contribute to the barrel length, SIG has opted to sell the rifle with a shorter actual barrel which has a large permanently affixed muzzle brake at the end.


The impetus for SIG’s lawsuit against the ATF was the bureau’s decision to classify the MPX muzzle brake as a silencer. Readers familiar with suppressors and other NFA devices will recognize that the ATF has determined that any part readily adapted to a silencer is indeed a silencer in and of itself. In practice this means that half of your local hardware store’s inventory could likely be classified as silencers or silencer parts if the ATF felt like it. A person with a threaded tube, some washers, and a few firearms might also be said to possess suppressor parts in the eyes of the ATF. Simply put, the standard by which the ATF determines what constitutes a suppressor is quite nebulous and open for interpretation.

This lack of clarity is precisely why the ATF’s ruling and subsequent legal response are so absurd. According to SIG’s filing, the device functions effectively as a muzzle brake, reducing felt recoil in a manner that is very similar to other products on the market. The only real difference between SIG’s offering and other muzzle brakes is its large size. What appears to have the ATF most concerned is the fact that it is also threaded on the end to afford users the option of adding a suppressor tube at a later date (with an approved NFA stamp). While this complaint seems legitimate at first glance, practically every suppressor manufacturer offers a quick-attach muzzle device designed to easily accept a suppressor. SIG is not inventing anything particularly new here; their product simply happens to be larger and configured a bit differently than other options.

Shortly after initiating the lawsuit, SIG offered the ATF a stay to give them time to look at the device a second time. During this time, the ATF received a sample of the MPX with muzzle brake and conducted testing to see how the device affected noise levels. Hilariously, the muzzle brake was found to actually increase the intensity of the firearm’s report by between 1 and 3 decibels, exactly the opposite from a functioning suppressor. Despite this discovery, the ATF has still maintained that it is a silencer and that its only purpose is to act as such. The ATF has yet to even address the muzzle brake’s merit as a recoil mitigation device. SIG now has until 11/1/2014 to respond the ATF ruling.

So why all the fuss and what is likely to come of it? According to USC 18 921(a), a silencer part is defined as “any part intended only for use” in a silencer. SIG’s argument is that the device is a muzzle brake that also can accept a silencer, thus it is not intended to serve only as a silencer. While the outcome of this lawsuit remains to be seen, it is encouraging to see SIG so steadfast in their case against the ATF’s arbitrary classification policies.


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