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When SIG SAUER introduced the MPX (their 9mm MP5 replacement), the plan was to have a long “muzzle brake” permanently attached to the end of the barrel to produce a “rifle” variant for civilian sales. The gun doesn’t run with long barrels, so it was the only viable solution to allow people to use a stock on their MPX. But there was also a trick: the muzzle brake could be turned into the baffle stack for a silencer by purchasing a proprietary shroud that only SIG can produce, which is legally registered as a silencer, and then affixing it to the gun. The ATF didn’t like that and classified the whole thing as a silencer, even the bare muzzle brake. SIG called bullshit and sued the ATF. Now it looks like that lawsuit is on hold, pending a re-examination . . .

While I’d love nothing more than to see the ATF taken to the judicial woodshed, second place is still good enough. In this case second place is that the ATF rescinds their classification and the MPX with a gigantic muzzle brake goes on sale as planned. According to, it looks like SIG SAUER has agreed to put its lawsuit on hold while the ATF gets a chance to re-consider their position and decide if they would rather back down or be beaten in court.

By agreement, approved by the U.S. District Court of New Hampshire, Sig will “stay” it’s lawsuit against the ATF until Sept. 17. In the meantime, both sides agree, Sig will send the ATF a sample of its muzzle brake for review and the ATF will issue a ruling, its third, by Aug. 6.

Faced with the federal lawsuit, which also names U.S. Attorney General Eric Holder as a defendant, the U.S. Attorney’s office notified Sig that it would reconsider its two prior decisions that call Sig’s muzzle brake an item “intended only for use” when making a silencer. The ATF asked the federal court to give it time to “review the matter and issue a new decision,” according to court records.

Terms of an agreement, filed with the federal court, say that if the ATF’s decision is agreeable to Sig, the Newington firearms manufacturer “will have obtained the relive sought without further litigation,” If the ATF again rules that Sig’s product is a silencer component, the federal civil suit will proceed, according to the agreement approved by federal Judge Paul Barbadaro.

SIG will win this legal battle one way or another, its just a matter of time and money. Some of my sources are telling me that in the wake of the Abramski Supreme Court case, the ATF is feeling a bit more froggy and might be going after other technically legal business practices in the near future under the guise of “public safety,” but I’m betting they will try to avoid picking fights with better funded legal teams in the future.

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      • I’m going to go against the tide here and say that I don’t see this working out well for SIG. If I was the ATF and this went to court, I would use the fact settled case law already agrees that 81% lowers are rifles. Well, arguably, this is 81% a suppressor. ALL of the machining steps have taken place.

        Add to the above that this is a NFA item, which has additional legal support for extra scrutiny.

        As Rab points out, it’s not an ATF determination that suggests parts of a suppressor are a suppressor, but rather rather it’s legislated – 18 U.S.C. § 921(a)(24)

        SIG is not an idiot, they have some good lawyers, but know they’re on shaky ground.

        • The assertion that a muzzle break is not a suppressor is quite reasonable. How about ruling that a suppressor is a suppressor and a receiver is a receiver, and parts are parts? The whole discussion is absurd. Sig making a muzzle brake that you can put a registered tube onto sure looks like a reasonable attempt to comply with a ridiculous set of laws.

          I hope the ATF is allowed to do the right thing and rule in favor of SIG. SIG has done more than enough to satisfy the absurd and pretentious set of laws relating to suppressors.

    • Only shrouds with “Sig-Brand” sheet metal and a “Sig-Weld” will do. You can totally not go buy some sheet metal and fabricate a silencer around those baffles.

      Similarly, you can totally not go buy some washers and a length of pipe, and do the same darn thing for any firearm you care to name that is suppressable.

      Anyone with some really basic tools can suppress anything. The fact that suppressors are an NFA item is an example of what a steaming pile the NFA is.

  1. That makes me want to buy another Sig. The new 227 is sweet. Maybe a 226 Tac Ops. Damn, my bills. I could buy so many guns – and replace the ones lost in the boating accident – if gas and groceries weren’t so expensive.

    Add Ares Armor as another company willing to go toe to toe with the ATF. And me as one of the guys who is a potential ATF target since I’ve done business with companies who don’t cover to the Feds.

    Why do we even need the ATF, anyways?

    • To make sure guns never fall into the wrong hands. Of course, that would require the ATF to know what “the right hands” would even look like, but it currently doesn’t know its @ss from its elbow, much less knowing that a muzzle brake attached to a pistol is a hell of a lot less important than making sure that they are not supplying Mexican drug lords with M16s

  2. If/When they win the battle with the ATF over this one, I will be first in line to buy.

    And I’ll probably even do the paperwork to get their supressor add-on.

    The way I figure it, the part to make the faux barrel into a supressor won’t be too expensive so this may be a relatively inexpensive way to get into NFA items (from a certain perspective).

    • And because of Sig’s design, you don’t have to pay the SBR stamp tax too, which you would otherwise have to do.

    • Make no mistake, this will NOT be an inexpensive way to break into the NFA game. I see a minimum 2k price tag for the rifle, and a 300.00+ tube, then 200.00 for the stamp. You could build a 9mm SBR, and buy a silencer for much less, including the 400.00 for 2 stamps.

      Not to mention that you could move the silencer between other hosts. Not gonna happen with the MPX.

  3. If they make an MPX-C in .45 ACP, I’ll buy one.

    If they don’t, I’ll have to express my support by purchasing a 227.

    But I’d rather do both.

    Yes, yes, I know, I’m irrationally fond of the fuddyfive. I am well aware. But I have money, which means my irrational fondness is worth catering to. 😉

  4. If I am correct, the ATF defines a suppressor to include “parts” of a suppressor. Since the “break” is truly a suppressor baffle stack when used with the rest of the suppressor parts, then, by definition, it is a suppressor and ATF correctly labeled it as such.

    • Just found it:

      For the purposes of the National Firearms Act the term Silencer is defined in 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.

      Looks to me that AFT is correct and SIG is not.

        • “including any combination of parts, designed or redesigned, and intended for the use in assembling or fabricating a firearm silencer”

          Seems perfectly clear to me. Did YOU read it?

        • He’s right. Here is the clincher:

          “only for use in such assembly or fabrication.”

          If it is also a muzzle break, then it is not “only for use in such assembly or fabrication.” I am a lawyer and I did not sleep at a Holiday Inn last night. Of course, the law can be whatever the judge determines it to be, but I’m sure Sig doesn’t hire chumps.

      • yes, if you leave out parts of the rule/law you can make it mean whatever you want. you are leaving out the last part.

        “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*.”

        the brake, as is, does nothing to muffle or diminish the report. by itself, it is not a silencer.
        Since it can be used without the shroud, it falls short of being “intended ONLY for use in [a silencer]”.

        the shroud might be a silencer part, it might be intended ONLY for that use. the brake is clearly not….by design.

        • Reverse clincher (Hypothetical) – If the ATF does a scientific evaluation and find that the last chamber(s) do nothing to assist with braking and are only of use if converted to a suppressor……..Then it’s not designed to be an effective muzzle brake, bur rather a suppressor.

          If the ATF can prove that the specific design of the end device was to facilitate conversion to a suppressor, then SIG might be out of luck.

          The first judge already ruled that the issue was that the ATF didn’t do a scientific/technical evaluation, not that the ATF was wrong……

      • I’m not sure, but I think you may have missed one caveat; “including any COMBINATION of parts”. I believe what they are manufacturing is a ‘shell’ into which other parts COULD be inserted. The so called, “shell” does not meet the definition of ‘part*s*’, since it is a complete assembly as distributed by the manufacturer as a part of the base weapon. Did I miss something?

      • “any part intended ONLY for use in such assembly or fabrication.” -of a suppressor that is.

        But we have all forgotten the REAL point here. The point of this “baffle stack” or “muzzle brake” isn’t to reduce muzzle blast, or to be part of a muffler, or to diminish recoil. The point of the permanently attached “brake” is to create a legal rifle.

        “a long “muzzle brake” permanently attached to the end of the barrel to produce a “rifle” variant”

        So its one part that can later be modified into part of a suppressor, but it was NOT intended as a suppressor. It was intended to increase the barrel length to 16 inches to make a legal rifle. Its main job is a barrel extension to meet the requirements of another ATF law. Barrel extensions are not suppressors. But, you could take a barrel extension and drill a lot of holes in it and cover it with another tube (spaced by supporting baffles) and have MADE a suppressor. That doesn’t make it a part of a suppressor. If it does, then we are all in a lot of trouble because Red Jacket proved you can make a BARREL into part of a suppressor when they started making “integrally suppressed AKs”.

  5. Really this is Sig just trolling the ATF. At trade show: “This is totally a baffle stack when you buy our branded shroud”. To the ATF: “Nah bro, that’s totally a muzzle break, no baffle stack here.”

    Beyond anything this is just an example of the stupidly of our laws. It’s not every day you wish for Oceanic or European style regulation where in many places a suppressor is considered an unregulated basic disposable wear item.

    • Don’t care. Sig gets points just for being willing to challenge the ATF instead of bending over and taking it. Even if they ultimately lose, at least they made the challenge.

      I own two Sigs. The debate at this point is if I’m going to end up owning three… or four.

  6. If the ATF is revisiting this issue again, then there’s a better than even chance that it will roll back its first two rulings. Otherwise, what would be the point of a third go-round?

    But if ATF doesn’t change its mind, then there’s a better than even chance that the court will uphold it.

    Courts are reluctant to set aside the rulings of agency “experts,” to which it grants great deference. If the ATF looks at an item three times and comes to the same conclusion three times, a court is very unlikely to tell an agency that it was wrong three times.

    • What most people fail to realize is that there is a precedent that places the burden on the experts (The ATF/FTB in this case) to demonstrate that the item in question that they are blocking the sale of needs to actually suppress or silence a weapon. A judge granted Innovator LLC summary judgment on its claim under the Administrative Procedure Act, holding that the agency’s action must be set aside as arbitrary and capricious because of the agency’s failure to “articulate a satisfactory explanation” and “examine the relevant data” in classifying Innovator’s Stabilizer Brake as a “firearm silencer.”

      • The court set the matter back to the ATF for further proceedings. Here’s the critical language by the court:

        “the Court holds only that the agency action must be set aside as “arbitrary and capricious” under the APA, due to ATF’s failure to “articulate a satisfactory explanation” and “examine the relevant data” in classifying Innovator’s Stabilizer Brake as a “firearm silencer.” That is not the same thing as actually holding that the Stabilizer Brake is not a silencer. The Court does not have enough information to determine whether the Stabilizer Brake is or is not a silencer; nor is it the Court’s responsibility to do so. The duty of making that determination—using a rational process—lies with the agency in the first instance.”

        Arbitrary and capricious is a very low bar for the ATF to hurdle.

  7. Argh! “Public safety” again! Somebody should tell those weenies that all known research and all known experience has shown that the highest level of public safety would be achieved by having the largest number of citizens armed. And of course, end Nixon’s insane racist War on (some) Drugs.

    • You do know that Nixon is dead, right?

      I prefer to think of the War on Drugs as the Nixon, Ford, Carter, Reagan, Bush, Clinton, Bush, Obama War on Drugs.

  8. Wow. That took longer than I expected it to. I can’t foresee any outcomes that are favourable for SIG Sauer. Anyone familiar with silencers would only associate this with the NFA item. It, in a way, reminds me of a sausage. The baffle-muzzle-brake-thingiemajiggie is the ground meat, but it only becomes a sausage when you add the skin. Would you really describe a cylindrical-shaped mass of ground meat as a sausage without the skin?

  9. “…a proprietary shroud that only SIG can produce…”

    Hilarious. Because only SIG Sauer possesses the ultra-advanced technology to make metal tubes, right?

  10. I appreciate the effort, on both sides ; )

    At least we get to try. : )

    What if you put a slide-fire stock on it and a hell-fire trigger? The ATF would stroke-out, and sales would be brisk.

  11. Will definitely pick up an mpx. Would prefer it in .45 ACP, but will pick up the 9mm one if they don’t. I’ve been eying the Sig556xi, but haven’t been able to pull the trigger. This looks like a better option to go with my SPR.

  12. The Germans are pissed off that they didn’t get their gold back so they’re going to fvck with us any way they can.

    • I think you’re thinking of the leprechaun from the movie “Leprechaun”. Now that’s a dude who seriously wants his gold back.

  13. It’s good that permission givers have to get permission to not give permission.
    The ATF act as if they are the boss of things.

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