The U.S. Department of Justice amended the regulations of the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) to clarify that bump-stock-type devices—meaning bump-fire stocks, slide-fire devices, and devices with certain similar characteristics—are machine-guns as defined by the National Firearms Act of 1934 and the Gun Control Act of 1968 because such devices allow a shooter of a semiautomatic firearm to initiate a continuous firing cycle with a single pull of the trigger.

Specifically, these devices convert an otherwise semiautomatic firearm into a machine-gun by functioning as a self-acting or self-regulating mechanism that harnesses the recoil energy of the semiautomatic firearm in a manner that allows the trigger to reset and continue firing without additional physical manipulation of the trigger by the shooter. Thus, a semiautomatic firearm to which a bump-stock-type device is attached is able to produce automatic fire with a single pull of the trigger.

With limited exceptions, the Gun Control Act makes it unlawful for any person to transfer or possess a machine-gun unless it was lawfully possessed prior to the effective date of the statute. The bump-stock-type devices covered by the Rule (published in the Federal Register at 83 FR 66514) were not in existence prior to the effective date of the statute and are prohibited upon the effective date of the Rule (March 26, 2019).

Under the Rule, current possessors of bump-stock-type devices are required to destroy the devices or abandon them at an ATF office prior to the effective date of the Rule.

In Wisconsin, as in the rest of the United States, bump-stock-type devices are classified as machine guns under the amended regulations of the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), as per the National Firearms Act of 1934 and the Gun Control Act of 1968. These devices, which include bump-fire stocks and slide-fire devices, enable a semiautomatic firearm to fire continuously with a single trigger pull, effectively converting it into a machine gun. The possession, transfer, or manufacture of machine guns is generally prohibited, with certain exceptions for those lawfully possessed before the effective date of the relevant statutes. The ATF rule, effective March 26, 2019, requires that all bump-stock-type devices be destroyed or surrendered to an ATF office prior to this date, as they were not in existence and thus could not have been lawfully possessed before the Gun Control Act came into effect. Violation of these regulations can result in legal penalties, including fines and imprisonment. Individuals in Wisconsin who possess such devices must comply with this federal regulation or face legal consequences.