Binary Triggers — What They Are, How They Work & Where They're Legal in 2026
Posted by Mendy Segelman on 11th May 2026
A binary trigger fires one round when the trigger is pulled and a second round when the trigger is released — two shots per trigger cycle instead of one. The result roughly doubles the practical rate of fire of a semi-automatic firearm without converting it to fully automatic and without running afoul of the National Firearms Act. Federally, binary triggers are legal. In approximately 17 states, they are not.
This guide covers exactly how binary triggers work mechanically, why they are federally legal, which states have banned them as of 2026, and what the two dominant platforms — Franklin Armory and Fostech — actually deliver.
How a Binary Trigger Works
A standard semi-automatic trigger fires one round on the trigger pull. The trigger then resets when released — but the release fires nothing. One pull, one shot, reset.
A binary trigger changes the release. In binary mode, the trigger fires one round on the pull and a second round on the release. Two separate physical actions, two separate rounds fired. The shooter controls the speed — there is no mechanical automation. The rate of fire is limited by how quickly the shooter can pull and release the trigger.
The critical safety feature on quality binary triggers is the cancel function. If the shooter pulls the trigger and enters binary mode, holding the trigger to the rear without releasing prevents the second round from firing. Switching the selector to semi-auto or safe while the trigger is held also cancels the release shot. This is a genuine safety mechanism — not a marketing claim — and it distinguishes quality binary triggers from less sophisticated designs. Both the Franklin Armory BFSIII and the Fostech Echo Sport include this cancel function.
Binary triggers are drop-in replacement components — they install into the same trigger group space as a standard mil-spec trigger without requiring permanent modification to the firearm. Installation typically takes 20-30 minutes with basic tools and no gunsmithing.
Why Binary Triggers Are Federally Legal
The federal definition of "machine gun" under 26 USC 5845(b) covers any weapon that fires "more than one shot, by a single function of the trigger." The ATF has consistently held that a pull and a release are two separate functions of the trigger — not one. Therefore, binary triggers do not meet the definition of a machine gun under federal law and are not regulated under the National Firearms Act.
This interpretation was confirmed in a March 2022 ATF open letter specifically addressing binary triggers, distinguishing them from bump stocks (which the ATF reclassified as machine guns in 2018). Binary triggers require two distinct physical actions per cycle. Bump stocks allowed a single trigger function to produce multiple shots through the recoil mechanism. The legal distinction is clear, and the ATF's position on binary triggers has remained consistent.
Franklin Armory patented the binary trigger mechanism in 2018 following years of development that began in 2015. The patent has driven significant litigation between Franklin Armory and competitor trigger manufacturers, but the federal legal status of binary triggers as a category has not been in dispute.
State-by-State Legal Status — 2026
Federal legality does not override state law. As of 2026, approximately 17 states and Washington D.C. ban binary triggers or devices that increase a semi-automatic firearm's rate of fire:
States where binary triggers are banned or restricted: California, Connecticut, Delaware, Hawaii, Illinois, Iowa, Maryland, Massachusetts, Minnesota*, New Jersey, New York, Oregon, Rhode Island, Virginia, Washington, and Washington D.C.
*Minnesota enacted a binary trigger ban in 2024. A state court struck down the ban in August 2025 on state constitutional grounds. As of May 2026 the legal status in Minnesota remains in flux — verify current status before purchasing.
The penalties vary significantly by state. Connecticut treats possession as a Class D felony. California classifies binary triggers as "multiburst trigger activators" under California Penal Code 32900, with violations carrying up to one year in county jail or a longer prison sentence depending on circumstances. New Jersey included binary triggers in its machine gun definition in 2019, making possession, sale, and transfer illegal.
If you live in any state not on this list, binary triggers are legal to purchase and possess under current state law. This list changes as states pass new legislation — always verify your state's current statutes before purchasing. For state-specific firearm restrictions, see our ammo and magazine laws guide.
Franklin Armory BFSIII vs Fostech Echo — The Two Platforms
Two manufacturers dominate the binary trigger market. Understanding the differences is worth the time before spending $300-$400 on a trigger group.
Franklin Armory BFSIII (Binary Firing System III) is the original and most widely used binary trigger. The three-position selector — safe, semi, binary — provides clean mode switching. The BFSIII is available for AR-15, AR-10, AK platforms, Ruger 10/22, and select pistol platforms including Glock variants. The AR-C1 variant fits most mil-spec AR-15 lowers without modification and is compatible with standard BCGs and upper configurations including .22LR, 9mm, and standard rifle calibers. The trigger pull in binary mode is consistent and crisp. The cancel function works reliably. Franklin Armory backs the BFSIII with a limited lifetime warranty.
Fostech Echo Sport is the primary competitor. The Echo uses a two-position selector — semi and binary — without a dedicated safe position (the firearm's standard safety handles safe engagement). The Echo has a reputation for a slightly lighter trigger pull than the BFSIII, which some shooters prefer. Compatibility with certain AR-15 lower configurations is occasionally reported as tighter than the BFSIII — verify compatibility with your specific lower before purchasing. The Echo is available for AR-15 and AK platforms.
Both triggers install in approximately 20-30 minutes and require no permanent modifications. Both include the cancel-on-release function. The BFSIII's three-position selector gives it a cleaner manual of arms for most shooters. The Echo's lighter pull appeals to shooters who want less resistance. Both are legitimate quality products at comparable price points.
Practical Considerations
Binary triggers are range-use accessories for most buyers. The doubled rate of fire is not a tactical advantage in defensive scenarios — it increases ammunition consumption without improving accuracy. At the range, running a binary trigger on a semi-automatic rifle is genuinely entertaining and provides a different shooting experience without the legal exposure of Class III machine gun ownership.
Ammunition consumption doubles in binary mode by definition. Budget accordingly for range sessions — what was a 30-round magazine's worth of shooting at comfortable pace becomes 60 rounds of equivalent trigger activity.
Most ranges allow binary triggers. Some ranges that cater to new shooters or operate in more restrictive jurisdictions may prohibit them — verify your range's rules before using one for the first time.
For AR-15 trigger selection across the full spectrum — from mil-spec to drop-in single-stage to binary — see our mil-spec vs upgraded trigger guide. For AR-15 platform guides, see our AR pistol guide and AR Pistol vs SBR comparison.
This article is for informational purposes only and does not constitute legal advice. Binary trigger laws change frequently at the state level. Always verify your state's current statutes before purchasing any firearm accessory. When in doubt, consult a qualified firearms attorney.
About the Author: Mendy Segelman is the owner of Tactical Surplus USA and a competitive shooter with over 10 years of experience in firearms retail.
For AR-15 owners pairing a binary trigger upgrade with other accessory improvements, the charging handle is the second-highest impact upgrade per dollar. See our charging handle buying guide for the Radian Raptor, BCM Gunfighter, and Geissele Airborne breakdown.