NEWINGTON - In the wake of a Bureau of Alcohol, Tobacco, Firearms and Explosives decision last month, that says a device gun maker Sig Sauer calls a "muzzle brake" is actually a silencer, Sig has filed an amended lawsuit against the ATF.

Filed Monday in the U.S. District Court of New Hampshire, Sig's two-count lawsuit asks a federal judge to "hold unlawful" ATF's decision as "arbitrary and capricious and not in accordance with law." Sig's lawsuit also asks the court to declare that its device is not intended only for use in making a silencer and to grant it costs, attorneys’ fees and "other relief... as appropriate."

Sig claims in its amended lawsuit that it designed a muzzle brake for commercial sale to the general public which reduces recoil and muzzle rise when a shot is fired. As such, it's not subject to regulation under the federal Gun Control Act, Sig claims. The GCA, according to Sig's suit, requires gun markers to mark firearms with serial numbers and other markings, to keep records of acquisitions and dispositions of firearms and "imposes controls on the interstate movement and the transfer of firearms." Sig wrote to the court that the National Firearms Act imposes similar regulations, but also imposes regulations on silencers.

Sig tells the court its muzzle brake does "not silence, muffle, diminish the report of a firearm" and if its classified as a silencer, it is subject to "burdensome legal requirements" including marking, record keeping and transfer restrictions.

"Under such classification, no market would exist for the muzzle brake because consumers would have no incentive to subject themselves to the required burdens and costs to purchase a device that does not function as a silencer," Sig's suit says.

"ATF did not dispute that the Sig Sauer device is an effective muzzle brake in that it diminishes recoil and muzzle rise," Sig's states. The gun maker claims it submitted data and DVDs to the ATF showing that its device, when attached to a rifle and extending its barrel to 16 inches, did reduce recoil, but did not reduce decibels.

Sig claims it has suffered economic harm by the federal designation, while telling the court the ATF failed to address "similar devices in the marketplace" that are sold as muzzle brakes and can be made into silencers with the addition of other materials. Sig also complains to the court that the federal agency acknowledged the Sig device can be used as a muzzle brake, while also claiming it is only intended for use as a silencer.

The ATF has not yet responded to the amended lawsuit, but previously responded to Sig's original complaint stating that Sig's device is constructed as a silencer component commonly referred to as a "monolithic baffle stack."