The rise of machine gun conversion devices (MCDs), commonly referred to as auto sears or Glock switches, represents one of the most pressing public safety threats facing communities today. These small, easily acquired devices can convert a standard semi-automatic handgun into an illegal fully automatic weapon capable of firing hundreds of rounds per minute. As their use continues to grow across the country, lawmakers and law enforcement agencies are mobilizing to respond. The convergence of updated state legislation and advanced gunfire detection technology signals a critical turning point in the effort to combat the growing threat of MCDs.
An Escalating Threat
Recent data from the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) shows a staggering 570% increase in the number of firearms equipped with conversion devices between 2017 and 2021. These devices are increasingly being linked to violent crime, including mass shootings and officer fatalities. Their accessibility, often available for under $100 online or produced with a 3D printer, makes them particularly dangerous.
State Legislation Steps In
Although federal law has long prohibited the possession of machine guns and conversion devices, the enforcement burden has historically fallen on federal agencies. This often can lead to delays and limited prosecutions. In recent months, however, more states are enacting laws that make possession of a Glock type switch a state-level felony, giving local law enforcement and district attorneys the authority to act swiftly.
In March 2025, Alabama Governor Kay Ivey signed SB116 into law, making possession or sale of a Glock switch a Class C felony punishable by up to 10 years in prison and a $15,000 fine. The law was passed with bipartisan support and prompted in part by recent tragedies, including the 2024 Birmingham nightclub shooting that left four dead and 17 injured. Madison County District Attorney Tim Gann emphasized the urgency of the legislation, noting the rise in local cases involving auto sears and the impact on officer safety.
Alabama joins a growing list of states taking legislative action. In early 2025, New Mexico enacted a similar ban, followed by Virginia and Mississippi. Other states, including New Jersey and California, are considering their own versions. What unites these efforts is a bipartisan consensus that these devices are too dangerous to be tolerated.
With that, the statute used by federal prosecutors is Title 26 USC 5845(b), which defines any parts designed to make a firearm fire multiple rounds with a single pull of the trigger as a machine gun by law. This legal foundation is often used in federal cases involving Glock type switches and other conversion devices.
The Role of Detection Technology
While legislative action is essential, it must be complemented by real-time detection tools that help law enforcement identify the use of MCDs in the field. Crime Gun Intelligence Technologies (CGIT) developed FireFLY, a gunshot detection and geolocation system that provides a critical advantage in this effort.
FireFLY can identify the distinct acoustic signature of automatic gunfire, distinguishing it from semi-automatic fire based on cadence. When an MCD is used in a shooting, FireFLY detects the rapid bursts and alerts officers in real time. What makes FireFLY particularly unique is that the system leverages a machine learning tool or specifically a deep learning model in addition to a signal processing classifier. This approach allows the system to analyze the acoustic characteristics of a shooting event and accurately predict whether the event involved machine gun fire.
This technology allows for faster, safer responses and increases situational awareness in high-threat environments. Additionally, the data collected by FireFLY can enhance national networks such as the National Integrated Ballistic Information Network (NIBIN) and the DOJ’s ANTI-MCD Task Force, allowing agencies to track patterns and link incidents across jurisdictions. This level of intelligence is critical for understanding the scope of MCD proliferation and for building strong, evidence-based prosecutions under new state laws.
Looking Ahead
The proliferation of machine gun conversion devices is a complex and evolving threat. As 3D printing technology and online marketplaces continue to make these parts more accessible, enforcement and detection strategies must adapt in tandem. The combination of new legislation and emerging technologies represents a coordinated and forward-thinking approach to public safety. By enabling local prosecution and equipping law enforcement with real-time detection tools like FireFLY, communities are better positioned to respond to the dangers posed by Glock type switches. Continued collaboration among federal, state, and private-sector partners will be essential to staying ahead of this trend.
Protecting communities requires both proactive policy and innovative solutions. With state leaders enacting meaningful legislation and technology providers delivering advanced detection capabilities, the national response to MCDs is gaining the momentum needed to make a difference.