This handgun can fire without anyone touching the trigger. That was the chilling bottom line of an FBI Ballistic Research Facility report that has sent shockwaves through the U.S. military and law enforcement circles, putting the Sig Sauer M18 the Air Force’s issue sidearm in unprecedented scrutiny. The discovery, revealed in July 2025, came weeks before the fatal accidental discharge of an M18 at F.E. Warren Air Force Base, when an incident fatally shot 21-year-old Security Forces Airman Brayden Lovan and prompted an immediate service-wide suspension of its use.
The M18 is the smaller version of the Army’s Modular Handgun System, modified from Sig Sauer’s P320 platform. It is a striker-fired, polymer-framed semi-automatic pistol with a modular fire control unit the serialized chassis that can be replaced by grip modules and slide assemblies. With military trim, it features several safeties such as a thumb safety, takedown safety lever, internal striker safety, disconnect safety, and loaded chamber indicator. The striker is semi-pre-tensioned in the course of chambering, a design feature that provides for a smooth trigger pull but one that leaves the firing system in a “ready-to-fire” position when resting.
The FBI review was precipitated by a July 2024 “uncommanded discharge” of a Michigan State Police M18 locked away in an Alien Gear Rapid Force Level 3 holster. The trigger was never touched, the officer and witnesses said. Technical examination found that the striker safety lock spring designed to prevent striker movement unless the trigger is pulled was not seated. The Bureau’s gunsmiths further discovered wear on the sear and its notches, and in controlled testing, they could fire primed cases by manipulating the slide and frame while manually releasing the sear, sometimes without trigger movement. In nine of about 50 such manipulations, the striker safety lock would not prevent ignition.
Sig Sauer contests these findings on the grounds that the FBI procedure punching the sear downward accidentally displaced the trigger bar and therefore did not produce an actual failure mode. The company further pointed out that making a viewing window in the slide to look at the spring eliminated structural support that otherwise holds it in place. In subsequent testing with a mutually accepted fixture, Sig reports the FBI was unable to cause a single unplanned discharge in 565 attempts over 19 striker assemblies. “The P320 CANNOT, under any circumstances, discharge without the trigger first being moved to the rear,” the company reported, citing testing by military, law enforcement, and independent laboratories.
Nevertheless, the FBI report and previous incidents have prompted prohibitions by several agencies, such as U.S. Immigration and Customs Enforcement, which reported an increase in accidental discharges following its adoption of the P320 platform in 2019. The Washington State Criminal Justice Training Commission also banned its use within training centers after experiencing six uncommanded discharges with M17 and M18 pistols at military installations since 2021, one of which was substantiated by “clear and convincing” video evidence.
From a purely engineering perspective, the debate is focused on the layered safeties of the striker-fired mechanism. In the M18, the primary and secondary sear notches restrain the striker, and the striker safety lock physically prevents forward motion. When sear engagement fails and the striker safety lock is deactivated due to component wear, incorrect assembly, or excessive torsional loads the last mechanical barrier in the system is removed. The FBI’s limited live-fire tests suggested that under certain manipulations mimicking duty conditions, this lock could be rendered inoperable. Sig counters that such conditions are either artificially induced or improbable in the field.
The Air Force’s procurement and testing history adds complexity. When the M18 was selected in 2017 to replace the Beretta M9, it underwent NATO-standard drop tests, environmental trials, and endurance firing. The military variant’s manual safety and trigger enhancements were specifically designed to prevent discharges if dropped. But the July 2025 fatality, coupled with the FBI’s findings, prompted Air Force Global Strike Command to order “100% inspections” of all M18s and suspend their use pending investigation. Air Combat Command also imposed restrictions, even as the Army, Navy, and Marine Corps continue to field the weapon.
Whether the Lovan incident was caused by a mechanical malfunction or operator error is inconclusive. An arrest on counts that include involuntary manslaughter indicates mishandling was a factor, but the technical argument over the M18’s design continues. For gun safety analysts, the incident highlights the thin line between mechanical protection, user training, and field realities. As one forensic engineering doctrine states: The discharge of a firearm in the absence of a depression of its trigger is evidence of a disabling defect… and must be prevented within the constraints of technical and economic feasibility.
