Yes. Auto sears are illegal for nearly all civilians under federal law. Federal statutes classify an auto sear as a “machinegun,” and possessing one without a pre-1986 federal registration is a felony carrying up to 10 years in prison and fines that can reach $250,000. The device does not have to be installed in a gun. It does not have to be fired. The part itself is the crime.
Why the Law Treats an Auto Sear as a Machine Gun
An auto sear is a small device that converts a semi-automatic firearm into one that fires continuously with a single trigger pull. It goes by several names: Glock switch, switch, drop-in auto sear, or DIAS. Most are small enough to fit in a pocket and can be installed without specialized tools.
Under both the National Firearms Act and the Gun Control Act, “machinegun” does not just mean a complete weapon. It also covers any part, or combination of parts, designed to convert a weapon into one that fires automatically.1Office of the Law Revision Counsel. 26 USC 5845 – Definitions The Gun Control Act uses the identical definition.2Office of the Law Revision Counsel. 18 USC 921 – Definitions An auto sear sitting in a drawer is legally the same as a fully assembled machine gun.
ATF formalized this classification in Ruling 81-4, which examined devices sold under names like “AR15 Auto Sear,” “Drop In Auto Sear,” and “Auto Sear II” and concluded they fit the statutory definition. Devices manufactured on or after November 1, 1981, became subject to all NFA requirements from that date forward.3Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). NFA Handbook – Appendix B – Rulings and ATF Articles The Supreme Court reaffirmed this treatment in its 2024 decision in Garland v. Cargill. While the Court held that bump stocks do not meet the statutory definition, the majority opinion specifically noted that auto sears do, and cited ATF Ruling 81-4 approvingly.4Supreme Court of the United States. Garland v. Cargill
The One Narrow Exception
Federal law does not ban every machine gun in existence. Under 18 U.S.C. § 922(o), two exceptions exist. The first covers transfers to or possession by government agencies. The second covers any machine gun “lawfully possessed before the date this subsection takes effect,” which was May 19, 1986, when the Firearm Owners’ Protection Act took effect.5Office of the Law Revision Counsel. 18 USC 922 – Unlawful Acts
A pre-1986 registered drop-in auto sear can still be legally owned and transferred between civilians, but it must remain registered in the National Firearms Registration and Transfer Record, and every NFA transfer requirement applies. The registry closed in 1986 to new civilian machine guns, so the supply is permanently fixed. That scarcity pushes prices for registered DIAS devices into the tens of thousands of dollars.6Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). National Firearms Act If you find an auto sear listed for a few hundred dollars, it is almost certainly unregistered and illegal to possess.
Federal Penalties for Simple Possession
Possessing an unregistered auto sear violates 26 U.S.C. § 5861(d), which makes it illegal to possess any NFA firearm not registered to you in the federal registry.7Office of the Law Revision Counsel. 26 USC 5861 – Prohibited Acts The penalty under 26 U.S.C. § 5871 is up to 10 years in prison and a fine of up to $10,000.8Office of the Law Revision Counsel. 26 USC 5871 – Penalties The general federal sentencing statute at 18 U.S.C. § 3571 allows fines up to $250,000 for any felony, and courts apply the greater amount. The realistic maximum fine is $250,000, not $10,000.9Office of the Law Revision Counsel. 18 USC 3571 – Sentence of Fine
The penalty applies whether the device is attached to a firearm or sitting loose. Because the federal definition treats the part itself as a machine gun, there is no defense based on not having installed it yet. A conviction also strips your right to possess any firearm going forward and creates a felony record that affects employment, housing, and voting rights in many states.
When Penalties Jump to 30 Years
Penalties escalate sharply if an auto sear intersects with another federal crime. Under 18 U.S.C. § 924(c), carrying or possessing a machine gun in connection with a crime of violence or a drug trafficking offense triggers a mandatory minimum of 30 years in federal prison, with no probation. That sentence runs consecutively to whatever you get for the underlying crime. A second machine gun offense under this section carries mandatory life imprisonment.10Office of the Law Revision Counsel. 18 USC 924 – Penalties
Simple possession under the NFA has no mandatory minimum, so a judge has discretion within the 0-to-10-year range. Once § 924(c) applies, the 30-year floor kicks in and the judge’s discretion largely disappears.
You Can Be Charged Without a Completed Device
The statutory definition of “machinegun” includes “any combination of parts from which a machinegun can be assembled if such parts are in the possession or under the control of a person.”1Office of the Law Revision Counsel. 26 USC 5845 – Definitions Having the components alongside a compatible firearm can be treated the same as possessing a completed device. Prosecutors do not have to prove you assembled them or intended to.
The same rule reaches homemade devices. The Department of Justice has specifically noted that individuals can make machine gun conversion devices through 3D printing, and the resulting devices are classified as machine guns under the same federal statutes.11Department of Justice. Machinegun Conversion Devices Making an unregistered machine gun violates 26 U.S.C. § 5861(f), and because the registry has been closed since 1986, there is no lawful way to register a homemade auto sear. Distributing CAD files designed for printing auto sears can also expose you to federal prosecution.
Ordering from an overseas seller adds a separate charge. Importing a machine gun conversion device violates 18 U.S.C. § 545, the federal smuggling statute, which carries up to 20 years in prison, twice the ceiling for domestic possession.12Office of the Law Revision Counsel. 18 USC 545 – Smuggling Goods Into the United States Customs records, shipping labels, and payment information create a clear evidence trail, and prosecutors have been stacking smuggling counts on top of NFA violations to push sentences well beyond the 10-year NFA ceiling.
Devices That Are Not Auto Sears
Not every aftermarket trigger device is a machine gun. The federal line depends on whether the device allows more than one shot per function of the trigger.
- Binary triggers fire one round when you pull the trigger and a second when you release it. Each shot corresponds to a separate trigger action, so they do not meet the federal machine gun definition. Some states independently ban them.
- Forced reset triggers were initially classified by ATF as machine guns, but in July 2024 a federal district court in Texas ruled that Rare Breed FRT-15s and Wide-Open Triggers are not machine guns under the NFA. The government entered a settlement and is returning seized devices to their owners.13Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). Rare Breed Triggers FRT-15s and Wide-Open Triggers WOTs Return
- Trigger cranks are manually operated assemblies that pull the trigger multiple times per rotation. Each shot still requires a separate trigger function, so they fall outside the federal definition.
The ATF settlement covers only eligible FRTs. Switches, drop-in auto sears, lightning links, and trigger control group travel reducers remain classified as machine guns and are unaffected by the FRT ruling. State laws vary, and some states ban binary triggers, FRTs, or other trigger-activating devices regardless of federal classification.
State Charges Can Stack on Top
Federal law sets the floor. Most state machine gun statutes mirror the federal definition and treat any conversion part as a machine gun; some define machine gun more broadly than the federal “solely and exclusively” language, and a handful of states have laws targeting auto sears and Glock switches by name.
State penalties are generally felonies, with maximum sentences ranging from a few years up to something approaching the federal 10-year ceiling. Federal and state prosecutors can pursue parallel cases from the same facts. That is not double jeopardy, because they are treated as separate sovereigns.
The Traps That Catch Buyers
The most common way people get charged is by not realizing the device alone is the crime. You do not need to fire it, install it, or even own a compatible firearm. Buying one out of curiosity, accepting one as a gift, or finding one in a parts lot you purchased can all result in federal felony charges. “I didn’t know what it was” rarely persuades prosecutors who can show you ordered it from a website advertising its function.
The other tell is the price. Legitimate pre-1986 registered auto sears cost tens of thousands of dollars because the supply is fixed. If you see a conversion device selling for $20 to $300, it is an unregistered machine gun. Purchasing it is a federal felony carrying up to 10 years in prison, and if it ships from overseas, you are also facing a potential 20-year smuggling charge on top of that.8Office of the Law Revision Counsel. 26 USC 5871 – Penalties