Sig MCX Extended Brake Ruled Suppressor by Judge

Sig Sauer has lost what is likely is first round of legal battles against the BATFE on the legal definition of the MCX’s “Muzzle Brake.” Granting summary judgement (a rare ruling typically on used when the judge believes the overwhelming or primae fascia evidence is in one party’s favor and that a trial would be a foregone conclusion).

The full ruling is available, but the juicy bits are boiled down below:

  • The judge agreed that it was the intent of the brake to be a suppressor.
  • The judge agreed with the ATF’s assertion that it was primarily  a baffle stack.
  • Judge agreed that muzzle brakes are functionally 2-3″ long.

In my mind, what is most worrying is the ATF continues to not disclose its test to determine if an item meets the NFA. Specifically, Sig sued as they believed the ruling was “arbitrary and capricious” as they did not have a formal framework by which to determine the items classification.

Rather than disclose its actual test, the ATF was successful at using a judge to make a determination. With the judge’s ruling, it will be difficult for Sig to challenge the ATF, as they would have to dispute a Judge’s ruling rather than the definition.

I hope they continue the good fight.

Nathan S

One of TFB’s resident Jarheads, Nathan now works within the firearms industry. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR’s, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.

The above post is my opinion and does not reflect the views of any company or organization.


  • dshield55

    Just need to get rid of the NFA and this wouldn’t be a problem in the first place. The damn thing should come with a silencer. It’s a women’s health issue because pregnant women can’t be around loud guns and yet the ATF continues their war on women. True story.

    • Menger40

      Hearing loss lasts a lifetime. Think of the children!!

    • Bill

      Seriously. Between the concussive sound and presence of heavy metals, I discourage pregnant women from the range. Not enough research has been done indicating whether it is safe or not.

    • Drew Coleman

      I think the hearing issue is secondary to potential heavy metal exposure (lead/mercury).

    • Sir TuberKopf

      There are several firearm regulations that blatantly discriminate against people outside average stature, as well as people with physical disabilities.

      I think is just criminal that the NRA doesn’t go to bat for these people.

      • dshield55

        Yeah, buying a collapsible stock for my 10/22 was the best thing I ever did for that rifle. It was finally comfortable for me (5’6″) and comfortable for nieces and nephews 5-10yo who had trouble shouldering the original stock.

        Not to sound absurd, but it would be neat if arthritis were a legitimate reason to repeal the Hughes Amendment. Who the hell wants to squeeze a trigger multiple times when they have arthritis? Squeeze once and let’er rip.

  • Matt in IL

    Summary judgments are not all that rare. Also, the standard, generally, to grant one is when there is no dispute as to all underlying questions of fact, and the movant is entitled to judgment as a matter of law.

  • hami

    It’s half of a suppressor not a muzzle brake. It was a good try, and I love the idea, but I can’t fault the ATF or the judge here.

    The real argument is why would a suppressor be this controlled in the first place. That is the problem.

    • KestrelBike

      Totally disagree. That’s like claiming a typical safe/semi AR lower is half of a “machine gun” thus class III. “But it’s just missing the sear!”
      Or a c/d cell maglight battery is half of a silencer, just waiting for the nefarious insertion of baffles.
      This was political BS by a judge supporting tyranny.

      • charlesrhamilton


      • KestrelBike

        Ah nevermind, aka_mythos shoots down my ar-MG comparison:

        “Multi-purpose use is why only some parts of an M-16 are considered machinegun parts by the ATF.”

      • hami

        If that AR lower has a sear hole drilled then yeah; under current law it’s half of a machine gun.

      • nova3930

        Or half the plumbing aisle at Lowes. I believe that in reality the law as written and applied to suppressors is unconstitutionally vague because there’s absolutely nothing special about a suppressor or its parts. Look around the average US garage and there’s a pile of suppressor parts. Got pvc pipe? That could be a suppressor. How about fender washers? Yep those too.

        Quite literally you can buy everything you need to build a suppressor off the shelf at Lowes for about $20 and all it takes to actually build it is a common drill. It won’t be pretty, very durable, or as size and weight efficient as a commercial model but it will do a fair job of reducing the sound signature of a firearm.

        • lucusloc

          I don’t actually know someone who built a muffler for his lawn mower that accidentally fit the bayonet mount for his nagant. True story.

          • iksnilol


            Never thought about using the bayonet mount for suppressors.

          • lucusloc

            A tight fit is necessary for it to work right. To the lawnmower I mean. I have no idea how well it will work for the Nagant. That is illegal don’t you know.

        • Bill

          You could say the same thing about building a meth lab or an IED. Let’s apply a little common sense.

          • nova3930

            It is applying common sense to insist on an objective standard to determine what is and is not a suppressor instead of letting ATF make it up as they go, especially as it pertains to the “collection of parts” which is unadulterated nonsense as I outlined above.

            We don’t go after Lowes for selling pipe bomb parts because they have 6″ threaded pipe nipple on the shelf and neither should we go after Sig by calling something that makes the gun louder a suppressor. That’s ludicrous.

            Simple, objective test.

            Does it reduce recoil? Yes
            Does it reduce sound signature? No

            Then it’s a brake. Reverse those and it’s a suppressor. How hard is that?

          • Bill

            It’s pretty hard when the brake is also a component of the suppressor they make.

            There IS precedent for the regulation of “precursors” that while they have legitimate, legal use are still controlled to one extent or another. That’s why you have to take the card off the rack and to the pharmacist to buy some cold medicines – it’s an ingredient of meth. Likewise for stuff like agricultural fertilizers like anhydrous ammonia and mining supplies like dynamite or other explosives.

          • nova3930

            And when you apply the “precursor” standard to suppressors you’re regulating tubing and fender washers. Just because precedent exists doesn’t mean it makes logical sense.

          • Bill

            Sometimes it does, sometimes it doesn’t: there’s Saddam’s “centrifuge tubes.” But the MPX “muzzle brake” is essentially an uncompleted SIG suppressor, so, like an auto sear, the fact that it does nothing on it’s own doesn’t mean it isn’t subject to regulation. Personally I think suppressors should be available out of vending machines, but until the administrative rules are changed, if you push the envelope far enough eventually it will rip.

      • skusmc

        This, and now a 2″ muzzle break welded onto a 14 inch barrel is actually an SBR since the builder obviously intends to turn it into one at some point, even if they intend to get a tax stamp first.

        Actual text of the NFA is irrelevant because the actual rule of law seems to mean little to a judge with an agenda.

    • lucusloc

      I can. Half a suppressor is not a suppressor. You cannot make something illegal if it does not do what the law says it is (stupidly) not allowed to do. This device does not suppress sound, therefor it is not a suppressor. It is in full compliance with the law. Do you know how many things we would have to ban if we adjusted the law to mean “can be easily made into a suppressor” like the judge has done here?

      • Joe B

        Even having part of a suppressor without approval is illegal isn’t it? It sure looks like a monocore baffle to me. I do agree, however, that the regulation of suppressors needs to be done with. He’ll, get rid of the entire NFA regulations.

        • lucusloc

          The problem is in defining what “part of a suppressor” is. Sig says this is a muzzle break. If it even marginally work in that capacity, then it is not “only” a suppressor part, it serves a dual purpose.

          The law is horribly written (by design), and needs to go, but this ruling is wrong even if we assume the law is correct.

          • tazman66gt

            by that reasoning any muzzle attachment that quick attaches a suppressor could be considered “part of a suppressor” and thus illegal.

          • lucusloc

            Why yes it does. If you want to be even more moronic you could say the threads on threaded barrels are part of a suppressor as well, because you need them to mount the suppressor. Hell, if we are throwing out the “only” part of “only used for suppressors” the barrels is part of the suppressor as well.

            Someone should write a letter asking the ATF about this. . .

      • LS1Y

        The statute in question is “[A]ny device for silencing, muffling, or diminishing
        the report of a portable firearm, including any
        combination of parts, designed or redesigned, and
        intended for use in assembling or fabricating a
        firearm silencer or firearm muffler, and any part
        intended only for use in such assembly or fabrication.”

        The judge points out that the applicable definition includes “any device for silencing” a firearm, any combination of parts “intended for use” in assembling a silencer, and any part “intended only for use” in a silencer. The baffle core fulfills at least the part about any part intended only for use in a silencer, as the Sig counsel admitted as much.

        • lucusloc

          actually, that is the sticking point, it was not “only”, it was in addition to functioning as a brake. If we read the strict letter of the law, since this device is dual use it does not fall under this provision, and this was one of the arguments sig made. Yes, you can use it as a baffle, but you can also use it is a brake. If you are willing to overlook the “only” in that law, that basically means everything is now legally a silencer.

          Of course since judges rarely interpret laws to mean what they actually say, the law actually means whatever the hell the judge wants it to, so this argument is moot no matter what the words are.

    • MANG

      The 2″-3″ criteria for muzzle devices is a bad precedent. It’s too bad SIG rolled the dice with this, because of course this is a suppressor core. So much “tee hee hee!” sophistic double talk is used to defend this product. I bet you SIG budgeted for the possibility of losing the case because they knew this outcome was so likely.

  • thedonn007

    Does it really matter if it is a muzzle brake? Does it or does it not suppress the sound of the firearm by at least 1 db? If it does then it is a suppressor, if it does not, then it is not a suppressor.

    • dshield55

      It actually makes the firearm slightly louder from what I remember about Sig’s brief in their lawsuit.

  • nova3930

    First “sound suppressor” in history that makes the gun louder

    • TheNotoriousIUD

      “Its ‘one’ louder.”

    • Nicks87

      Yep and 2 + 2 = 5.

      • TomOakheart

        1984 reference ftw.

  • Matt

    18 U.S.C., § 921(A)(24)

    The term “Firearm Silencer” or “Firearm Muffler” means any device for silencing, muffling, or diminishing the report of a portable firearm, including any combination of parts, designed or redesigned, and intended for the use in assembling or fabricating a firearm silencer or firearm muffler, any part intended only for use in such assembly or fabrication.

    By this definition the attachment would be termed a “firearm muffler”

    • aka_mythos

      If it does in fact function as a muzzlebrake doesn’t that factually mean the part isn’t “intended ONLY” as in singularly as a suppressor component?

      Multi-purpose use is why only some parts of an M-16 are considered machinegun parts by the ATF.

    • tazman66gt

      So then by that definition any flash suppressor, muzzle brake, or compensator that can attach a suppressor is then a suppressor.

      • Cymond

        Years ago, YHM was told to stop seeking the QD mounts for their pistol suppressor. The mounts were solely for mounting suppressors and served no other function.

        Later, they developed a new QD pistol suppressor, but they also offered QD brakes for the same mounting system. Those aren’t on the website anymore, but you may note that all of their current QD mounts are also flash suppressors.

        Yes, there are several QD rimfire suppressors on the market right now. The mounts serve no other purpose but to mount a suppressor. I have no idea how those are allowed.

  • Bill

    I believe the issue is that the brake forms the chassis of an easily constructed suppressor, and as a component is regulated. SIG has been playing fast and loose with the letter of the law, albeit creatively, and the laws may be pointless, but until they gets some legislative horsepower behind them they are just poking the bear.

    • aka_mythos

      How easily constructed, is easily constructed? Assuming this can actually function as baffles, it seems like someone would still need a machine shop and a variety of tools and skills. Under the assumption there are more steps between building this into a suppressor than turning an AR15 into a machinegun.

      Do we even know if this is built of the common materials suppressor baffles are made from? This could well fail if it’s for example aluminum and shrouded into a suppressor.

      • J.T.

        To answer your second question, this is taken directly from the ruling.

        “First, it is undisputed that the baffle core is an essential silencer component. Tr. at 55-56 (Doc. No. 31). It is, in fact, identical in design and dimension to the baffle core contained inside a removable Sig Sauer silencer. A.R. 824; see also Tr. at 55-56 (Sig Sauer’s counsel conceding that Sig Sauer has “basically taken the cap off [its] silencer . . . welded it into the gun, and [marketed the baffle core] as a muzzle brake”).”

  • aka_mythos

    I think fighting the judges ruling won’t be as hard as it could be… The three statements of the ruling can be argued against… Even if they are effectively baffles they are designed with the primary purpose of being a muzzle brake, where the NFA only regulates silencer parts when they can only be used for a suppressor. The third statement implies the judge made the ruling on the false notion that a muzzlebrakes are only 2-3″ long and not on any functionally technical merits. The reality is you can design a muzzle brake of any size or for any caliber and thus end up with something larger than three inches and this precludes the possibility of a future design contrary to the current norm.

    This will only lead to the ATF ruling all muzzlebrakes greater than 3″ are illegal on the pretext that a suppressor could be made.

    • Glock Guy

      Well said.

    • nadnerbus

      Yeah, wouldn’t that definition make all the .50 BMG brakes suppressors?

    • GaryOlson

      Stop giving them ideas! The ATF creates enough pointless bizarre logic without you helping them out.

  • dshield55

    So… Ares Armor has their Ares Breath muzzle break which is 6″ long that’s virtually similar to Sig’s except it has straight instead of slanted baffels. They HAVE NOT sent it into the ATF for review, but have been selling it for at least several monthy. Their website bases it’s legality on determinations letters that they’ve viewd and the fact that it has no threads for a sleeve and the have these little nubs that would prevent a sleeve from being applied. Rather than Sig giving up on their design and intentions completely, I’d suggest they just follow ARES’ lead. The nubs are easy enough to grind off and polish, and plenty of competent gun smiths can thread it when you get your paperwork back.

    • aka_mythos

      SIG’s position has been that it desires to comply with regulation but that the ATF refuses to provide clear guidelines. The ATF uses these determination letters because they aren’t legally binding and leave them with the sole discretion to unilaterally change their mind. When it comes to the ATF changing its mind there is little recourse, particularly with determination letters, because of the courts lack of willingness to get into the bureaucratic mess. The NFA is all the worse parts of tax law coupled with the technical challenges of patent law and in both of those instances they requires specialized judges with expertise in those area of law.

      • lucusloc

        It is a mess by design.

  • sean

    Maybe instead of trying to be sneaky and look for ways around laws….you spend that money on getting the stupid law overturned. Suppressors shouldn’t be a tax stamp item.

    • aka_mythos

      I agree, but there are many fronts to a war. Those opposed to us having these rights will argue a moral high ground and argue how much we are in the minority. By having ubiquitous weapons and devices that sidestep the law we build a body of proof to contradict and undermine their “moral high ground” position. This approach allows larger companies that are more sensitive to political correctness to further a cause under the auspices of common business interest.

    • Vitsaus

      I agree, or spend the money or quality R&D instead of abelone shell finishes on your .380 carry guns, or rattlesnake skin grips. Or about about spending the money on a decent 550 series variant for the US market instead of a ton of half assed incremental “improvements.”

    • lucusloc

      Making them define their law into absurdity is part of the process.

  • Can we just get one with a normal 16″ barrel please?

    • Blake

      You mean the MCX Carbine?

      • In 9mm?

        • Blake

          so, I just noticed that all the text in the article refers to the “MCX” but the graphic (& the ruling) refer to the “MPX”, which indeed isn’t listed on Sig’s site with a 16″ bbl…

  • Joe

    Or, you could have a 16″ barrel and benefit from this odd concept of “muzzle velocity” rather than pinning an oversized brake to your otherwise SBR length barrel. Or, option 2, just do it as a legal SBR and ditch the oversized brake altogether.

    • Cymond

      It’s a 9mm, they don’t benefit much past about 10-12″.

  • DIR911911 .

    the stupid are definitely outbreeding the smart

    • Bacon Chaser

      Its only a matter of time before Idiocracy becomes a documentary instead of a comedy.

  • iksnilol

    I don’t know much law, but isn’t a suppressor/silencer (legally) something that reduces the sound the firearm makes?

    So put this next to a soundmeter, check if it actually reduces sound and go from there.

    NOTE: what I wrote probably makes too much sense, right?

    • lucusloc

      For the ATF? Why yes it does.

  • smelly

    Land of the free my as#

  • Rick5555

    Nathan S., it’s quite unfortunate, that in our legal system. It is not what you know, but rather what you can prove. That is how our system works today…in civil and criminal court. It’s why it’s always wise to obtain really good legal counsel. One of my brothers is a prominent attorney in Nashville. And he always tells me…it’s what you can prove or disprove that matters. Doesn’t matter, how the law is written per se.

  • Cal.Bar

    This weapon has been a real problem from the start. First the “sig brace” for it, then the muzzle break. Didn’t anyone with Sig vet these things with the ATF before rolling them out and marketing them to the public. Makes a major firearms MFG look bad (no matter how asinine the Fed. rulings)

    • lucusloc

      ATF does not really do that. They want you to complete the product before they issue an opinion on it. They also reserve the right to change their mind.

      • Tim Pearce

        As I’ve heard it described, they don’t fully explain what the rules the manufacturer has to play by are. They sometimes just say, “nope! try again!” and refuse to explain what criteria the gun failed to meet.

        • lucusloc

          that is a much better way to put it, yes.

        • Bill

          Sure they explain what rules are, and they fill volumes that anyone can access. It’s manufacturers and users who try to push the envelope that bring this stuff on themselves. Before the SIG brace fiasco and now this how often did anyone hear of the ATF doing stuff like this?

          • lucusloc

            The rules are intentionally vague and capricious. The less they define what you can and cannot do the more leeway they have when they want to infringe on our rights. That is how we get rulings that define and object that does not diminish the report of a rifle as a silencer.

            Sig had a good marketing idea that would get more people to get into ATF stamp collecting. You buy all the major parts now, free and clear, and then file the paperwork for your stamp. When the stamp comes sig gives you the final bit for basically no extra cost. Sig even followed the exact letter of the law, because the part in question was dual use, and so was not “only” part of a suppressor (as it was also a brake).

            This was a problem for the ATF, since more people getting into stamp collecting means more people are aware how absurd it is, which means more political pressure to scrap the system. So they went to a friendly judge who would trow out the letter of the law and rule in the spirit of it (hint, the spirit of the law is to infringe on our rights).

            The sig brace is another example of this battle, but on the SBR side of things. The more we force the ATF to define exactly what the law means, the less they can wiggle their way around how absurd these laws actually are. The more outrageous their rulings are the better our chances of getting the whole thing scrapped.
            Honestly we should all be looking for gaps in their rulings, and force them to define every last little thing as legal or illegal.

            ATF says sig brace is ok, unless you hold it wrong, then it’s magically an SBR. Where exactly is that line? The shoulder joint? The elbow? How “wrong” does my grip have to be before I am a felon? ATF says the MCX is a silencer. OK what about other finned brakes? Are we going to define any finned brake over a certain length as a silencer? We wont know unless we force the ATF to respond. Technically this was also a circumvention of SBRs as well, might as well ask what kind of barrel extensions are illegal. Submit a letter for every last one of them. If any are denied take it to court and get a ruling on it. It does not matter if we lose, every fine line they draw brings us closer to final victory.

            If we let these line stay as big wavy grey zones they win, because they can twist thing to sound reasonable to average people. If we get fine lines defined in actual law, rather than opinion letters we can ask people why one thing is on one side of the line, and another almost identical thing is on the other. That kind of thing make even people not all that into the issue think and ask more questions.

          • Bill

            …and when we get precise, definitive laws that cover every bit of detail we can complain about zero-tolerance….

          • lucusloc

            Good point. Hit these laws any way we can. The only way we are going to defeat them is with public support.

      • Cal.Bar

        Actually, like the IRS and other Federal Agencies, they DO issue advisory opinions. I just don;t know if Sig bothered to get them in this case

  • RICH

    Leave it to the ‘G’ to screw up anything they can without reason ! ! I worked side by side with the ALPHABET groups for many years…..and they just never seem to better themselves.

  • nobody

    Considering how US law considers a suppressor baffle stack by itself to be a suppressor and how Sig intended to sell a threaded tube designed to go over this “muzzle brake” and use it as a baffle stack in a suppressor, it was obvious how this case would turn out from the beginning. While I don’t like the NFA and think suppressors should be completely unregulated like they are in Europe, this lawsuit is ridiculous. Now when is the NRA finally going to get around to that campaign about deregulating suppressors that they were supposedly gearing up for a few years ago.

    • lucusloc

      The problem is that according to the actual, horribly written and unjust law, in order to be considered a suppressor the part has to be suitable “only” for use as a suppressor part. Since this is quite clearly not just a baffle stack, but is also a break the part of the law that defines what a suppressor part is cannot apply to this object.

      Of course if we take into account how US law works (as you said), that law actually means whatever the judge wants it to mean, with no regard for what the words (badly written and unjust or not) actually mean.

      Since no one knows what the law actually means until some judge makes a decree, we are no longer a nation of laws, but rather are a nation of men, ruled by other men (typically judges).

  • lucusloc

    Sorry, I was not trying to imply anyone here was a moron. That barb was targeted at the ATF.

  • Shmoe

    You should be able to buy a “silencer” off the shelf at Walmart, How they, in any way, represent a threat to the public is a complete mystery to me.

  • Democrats; an endangered feces

    No use in wasting good money on court cases as long as Obama is in office.

    Sig might has well presented their case to a panel composed of Lois Lerner, Hillary Clinton and Diane Feinstein. They would have had about the same level of success.

    Gun manufacturers would do well to ease up on pushing items like suppressors and such temporarily. With the latest college killing, the gun haters are frothing at the mouth to do whatever damage they can to the Second Amendment, and Lord knows that Obama is prepping for a ‘Hail Mary’ level of anti-gun legislation before he slithers out of office.

  • CavScout

    WHO CARES, give me the .40S&W MPX already!

  • Mike

    Not surprised at all with the common sense ruling.

    • lucusloc

      you mean the ruling that threw out the letter of the law in favor of pushing an agenda to infringe on our rights?

  • Bodie

    Can you guys PLEASE do something about how freaking massive the “Subscribe to our twice-weekly newsletter:” banner is. It takes up far too much of the page, and can clearly be condensed. It is such a freaking nuisance and irrationally large. I get to your articles BECAUSE of your twice-weekly newsletter that I am subscribed to. I don’t understand why the “Subscribe to our twice-weekly newsletter:” isn’t aligned with the “Type your e-mail here to subscribe” box and the “SUBSCRIBE” submission button. It’s off center, thus creating a need for a larger banner; the size of the font, email box, and subscribe button are freaking massive for absolutely no reason; and there’s a large amount of wasteful space above and below the print, email box, and submission button.

    Horizontal header/footer banners like these take up a large amount of space on the viewable screen. If you’re going to stoop the the level of low-grade advertisers that plague pretty much 99% of the webpages linked to on Facebook, which are all nothing but low intelligence garbage to get their matching social media audience to click so they can receive revenue from the 800 advertisers they have slowing each page to a dial-up internet connection crawl, the least you can do is make the banner as least intrusive and obnoxious as possible. I mean truly, it is so irrationally large that you might as well have just made it take up the bottom 50% of the screen, let the top browser toolbar take up the top 15% of the viewable screen, maybe even add in a second header banner just to draw more attention away from the page’s actual content, and leave the site visitors with 20% of the screen to view what’s on the page. I don’t really like not having to constantly scroll anyway. I like to read a single line of text, then have to scroll to center the next line of text to make it readable, and so on and so on. Having to not continuously scroll and scroll and scroll is boring and takes too quick to read an article. Bigger! Wider! More dead space! Less viewer friendly pages!