A small device that converts a handgun to fire automatically, often called a “Glock switch,” “auto sear,” or “conversion device,” is itself legally a machine gun. Possessing one, even without a gun, is a federal felony carrying up to 10 years, and a machine gun tied to a drug or violent crime triggers a 30-year mandatory minimum.
This guide explains how federal law defines a machine gun, the penalties under 18 U.S.C. § 922(o) and § 924(c), and how these cases are defended in the Eastern and Western Districts of Missouri.
The definition
Is a Glock switch a machine gun under federal law?
Yes. The definition includes conversion parts.
Under 26 U.S.C. § 5845(b), a “machinegun” is any weapon that shoots, is designed to shoot, or can readily be restored to shoot automatically more than one shot, without manual reloading, by a single function of the trigger. The definition also expressly includes:
- The frame or receiver of such a weapon;
- Any part designed and intended solely and exclusively for use in converting a weapon into a machine gun; and
- Any combination of parts from which a machine gun can be assembled, if they are in a person’s possession or control.
A conversion device, whether a manufactured switch or a 3D-printed one, falls within that definition by itself. The Supreme Court held in Garland v. Cargill (2024) that bump stocks are not machine guns because they do not make a gun fire more than one shot per function of the trigger, but that decision does not change the treatment of devices that convert a gun to true automatic fire.
Penalties
What is the penalty for possessing a machine gun?
Up to 10 years, and far more if connected to another crime.
Possession, 922(o)
Transferring or possessing a machine gun, other than one lawfully possessed before 1986 or by government authority, carries up to 10 years under 18 U.S.C. § 924(a)(2).
With a drug or violent crime, 924(c)
Using, carrying, or possessing a machine gun in connection with a drug trafficking crime or crime of violence carries a mandatory minimum of 30 years, consecutive to any other sentence.
National Firearms Act
Possessing an unregistered machine gun can also be charged under the National Firearms Act, which carries its own penalties.
Prohibited persons
A person prohibited from having firearms faces an additional felon-in-possession count, with up to 15 years.
How cases start
How do machine gun cases usually begin?
Often as a state gun or drug case.
Many of these cases start with a traffic stop or search warrant in a state case, where officers find a handgun with a conversion device attached or a loose switch. Because federal penalties are much higher, these cases are frequently referred to federal prosecutors. ATF examiners typically test-fire the weapon or device to confirm it functions as a machine gun.
Defenses
How do you defend a machine gun charge?
Function, knowledge, possession, and the search.
- Function. The government must prove the device or weapon actually fires automatically, or can readily be restored to. Test-fire procedures and results can be examined.
- Knowledge. The government generally must prove the person knew the weapon had the characteristics that made it a machine gun. A person who did not know a gun had been converted has a real defense.
- Possession. In shared cars and homes, knowing possession must be proven.
- The search. As with any gun case, suppression can end the case.
- The 924(c) count. Because the 30-year minimum is so severe, whether it is charged and whether it can be proven drive everything else.
FAQ
Machine gun and switch questions
Is having a Glock switch without a gun illegal?
Yes. A part designed solely to convert a weapon to automatic fire is itself a machine gun under federal law, so possessing the switch alone is a federal felony.
What is the sentence for a Glock switch?
Up to 10 years for possession under 18 U.S.C. § 922(o). If connected to a drug trafficking crime or crime of violence, § 924(c) adds a 30-year mandatory minimum, consecutive.
Are bump stocks machine guns?
No. The Supreme Court held in Garland v. Cargill (2024) that bump stocks do not make a firearm a machine gun under federal law.
Is a 3D-printed switch treated differently?
No. If it is designed to convert a weapon to automatic fire, it is a machine gun regardless of how it was made.
Can a machine gun case be charged in Missouri state court?
Missouri has its own weapons laws, but machine gun and conversion device cases are commonly prosecuted federally because of the federal statutes and penalties.
See our federal criminal defense and weapons defense pages, or call 573-638-8529.
Talk to us
A small part can carry a large sentence.
If you are facing a machine gun or conversion device charge in Missouri, call before your first court date.
Attorney advertising. The choice of a lawyer is an important decision and should not be based solely upon advertisements. This article is general information about federal firearm law as of October 2026, not legal advice, and it does not create an attorney-client relationship. The outcome of any case depends on its facts.
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