Binary triggers are legal in Tennessee. Neither federal law nor Tennessee state law treats a binary trigger as a machine gun, because each pull and each release of the trigger counts as a separate firing action. You can buy one, own one, and install it on your rifle without violating state or federal law as things stand in 2026. The caution worth carrying into the rest of this article is that trigger modifications sit in a shifting area of the law, and the devices that look similar to binary triggers are often the ones that will land you in prison.
Why a Binary Trigger Isn’t a Machine Gun
A standard semi-automatic trigger fires one round when you pull it and does nothing when you release it. A binary trigger adds a second firing event: one round on the pull, one round on the release. Two shots per full cycle, but each shot requires a distinct physical action from the shooter. Most binary triggers also include a selector that lets you switch between standard semi-auto and binary mode, and flipping back to semi-auto mid-cycle will cancel the release shot.
Federal law defines a machine gun as any weapon that shoots “automatically more than one shot, without manual reloading, by a single function of the trigger.”1Office of the Law Revision Counsel. 26 USC 5845 – Definitions The ATF treats the pull and the release as two separate functions, each producing one shot, and has confirmed this reading through private letter rulings issued to binary trigger manufacturers. Those rulings apply to the specific devices examined and the ATF could revisit them, but for now binary triggers remain federally lawful.
How Tennessee’s Statute Handles It
Tennessee defines a machine gun as “any firearm that is capable of shooting more than two shots automatically, without manual reloading, by a single function of the trigger.”2Justia. Tennessee Code 39-17-1301 – Part Definitions The state threshold is actually a touch more permissive than the federal one, which captures any weapon firing more than one shot per trigger function.
A binary trigger falls well short of either standard. It fires exactly one round per trigger function, counting the pull and the release each as a function. Two shots per cycle, one shot per action. That puts binary triggers squarely outside Tennessee’s machine gun definition.
Devices That Will Get You Charged
The real legal risk around trigger modifications is confusing a binary trigger with a device that genuinely converts a firearm to automatic fire. Three categories are worth knowing cold.
- Forced reset triggers. These mechanically force the trigger forward after each shot at a speed that mimics automatic fire. The ATF has classified several models as machine guns, concluding they produce more than one shot with a single continuous pull. A binary trigger uses a true two-action cycle; a forced reset trigger doesn’t, and owning one carries serious federal criminal exposure.
- Auto sears and Glock switches. These small conversion devices turn a semi-automatic firearm into a fully automatic one. A Glock switch lets a handgun empty its magazine on a single trigger pull. They are unambiguously machine guns under federal and Tennessee law. Tennessee’s HB 1093/SB 1075, passed in 2025, specifically expanded the state’s machine gun provisions and increased the penalties for possession.
- Bump stocks. These use recoil to let the firearm slide against the shooter’s trigger finger, producing rapid fire. Federal courts have gone back and forth on bump stock regulation in recent years, and several states ban them separately.
A binary trigger does none of these things. It doesn’t enable automatic fire, doesn’t force a mechanical reset, and doesn’t harness recoil. Each shot still requires a deliberate action from you.
What a Real Machine Gun Charge Looks Like in Tennessee
Intentionally or knowingly possessing, manufacturing, transporting, or selling a machine gun is a criminal offense under Tennessee law.3Justia. Tennessee Code 39-17-1302 – Prohibited Weapons Under the 2024 code the offense was a Class E felony, carrying a prison sentence from one to six years depending on the offender’s criminal history and sentencing range.4Justia. Tennessee Code 40-35-112 – Sentence Ranges The 2025 Glock switch legislation (HB 1093) increased the penalty to a Class C felony, with significantly steeper prison time. A felony conviction also strips your right to possess firearms at all.
Tennessee does recognize narrow exemptions, mainly for items possessed in full compliance with the National Firearms Act (which in practice covers pre-1986 registered machine guns with a valid NFA tax stamp), and for active-duty military, law enforcement, and corrections officers acting in their official capacities.3Justia. Tennessee Code 39-17-1302 – Prohibited Weapons None of this applies to binary triggers, since binary triggers aren’t prohibited to begin with.
What to Watch Going Forward
Buying, owning, and installing a binary trigger is legal in Tennessee as of 2026. The bigger practical risk is accidentally acquiring something that crosses the line. A device marketed as a “trigger upgrade” that actually enables automatic fire is a machine gun regardless of how the seller describes it. If a product claims to dramatically increase your rate of fire through a mechanism that doesn’t require a separate deliberate action for each shot, treat it with real caution. Tennessee has shown a willingness to tighten its laws around trigger modifications, and “I didn’t know it was a machine gun” is not a defense state courts will accept.