FBI Investigation Reveals SIG Sauer M18 'Uncommanded Discharge' Details

Federal Bureau of Investigation Makes Report Public

A comprehensive FBI evaluation has been released to the public, documenting findings related to a Michigan State Police officer's SIG Sauer M18 pistol that discharged without deliberate trigger activation. The M18 platform shares the same fundamental design as the commercially available P320 model, making these findings particularly significant for the broader firearms community.

Detailed Analysis of the Incident

Technical Findings from FBI Testing

The newly released 32-page report provides extensive documentation of the FBI's investigation into the uncommanded discharge event. Key findings include:

• Confirmed uncommanded discharge - The M18 pistol fired without the trigger being deliberately pulled
• Safety system analysis - Despite multiple integrated safeties in SIG's striker-fired system, vulnerabilities were identified
• Reproduction of the malfunction - FBI testing successfully replicated the issue under controlled conditions

FBI Ballistic Research Facility Results

The FBI's Ballistic Research Facility conducted thorough testing that yielded concerning results:

• New pistol testing - Even a brand-new M18 exhibited the same problematic behavior
• Systematic failure mode - Normal law enforcement officer movements can render the striker safety lock ineffective
• Sear failure implications - When the sear fails, the striker can impact a chambered round despite safety mechanisms

Real-World Implications for Law Enforcement

Everyday Carry Concerns

The FBI's findings highlight potential risks during routine law enforcement activities:

• Movement-induced failures - Standard officer movements can compromise safety systems
• Carry condition vulnerabilities - Risks associated with everyday holstering and movement
• Operational safety questions - Implications for departments using the M18/P320 platform

Previous Safety Concerns

This report adds to existing scrutiny of the SIG Sauer platform:

• Prior litigation - The M18/P320 has faced multiple lawsuits regarding safety concerns
• Drop safety questions - Previous investigations into drop-related discharge incidents
• Design scrutiny - Ongoing evaluation of the pistol's safety mechanisms

Impact on SIG Sauer

FBI's Official Position

The federal investigation maintains a measured approach to assigning responsibility:

• No negligence determination - The FBI has not declared SIG Sauer negligent in their findings
• Technical documentation - The report focuses on mechanical analysis rather than fault assignment
• Objective evaluation - Emphasis on documented testing results and technical observations

Industry Implications

The public release of this report creates several challenges for SIG Sauer:

• Design scrutiny intensification - Renewed focus on M18/P320 safety systems
• Real-world performance questions - Evaluation of safety mechanisms under actual use conditions
• Market confidence considerations - Potential impact on law enforcement and civilian adoption

Future Considerations

Ongoing Evaluation

The FBI report represents a significant development in the ongoing evaluation of striker-fired pistol safety systems. While no single defect was identified as the root cause, the documented possibility of uncommanded discharge during routine carry presents serious considerations for users of the M18/P320 platform.

The technical findings provide valuable data for understanding how modern pistol safety systems perform under real-world conditions, particularly in law enforcement applications where reliability and safety are paramount concerns.

Key Points from the FBI Report on SIG Sauer M18 Uncommanded Discharge

Incident Summary

• Date: July 31, 2024
• Location: Michigan State Police squad area
• Issue: SIG Sauer M18 pistol fired while holstered without trigger being pressed
• Officer: Had keys in hands at time of incident
• Weapon: M18 (mechanically identical to P320) with ~1,300 rounds fired

Critical Technical Findings

1. Striker Safety Lock Spring Design Flaw

• Spring was not fully seated on its post
• Only captured at top of striker housing (design limitation)
• Pre-upgrade P320 had both top and bottom capture points
• Spring can slip off, rendering striker safety lock inoperable
• Spring movement observed during all firing tests

2. Parts Wear Analysis

• Sear wear appeared off-center
• Primary and secondary sear notch edges showed excessive wear
• Striker pin hook had "ledge" instead of flat surface
• Reduced engagement surface between critical components
• Trigger guard abrasion consistent with key contact

3. Holster Vulnerability

• FBI successfully pressed trigger using keys while pistol was holstered
• Keys (1.7" and 1.0" length) could fully actuate trigger
• Holster design allows foreign object entry
• No damage to holster from uncommanded discharge

Laboratory Testing Results

Live Fire Testing

• 50 rounds fired: Striker safety lock spring moved every time
• High-speed video: Documented sear bounce and component interactions
• Secondary sear notch: Functioned properly in controlled tests

Striker Safety Lock Failure Testing

• Initial tests (100 attempts each): 0 failures
• Manipulation testing (50 attempts):
  • 9 successful fires (primer indentation 0.019"-0.026")
  • 6 partial strikes (primer indentation 0.0005"-0.001")
• Critical finding: 1 fire occurred with NO manipulation during staged test
• Brand new M18: Failed on second attempt (primer indentation 0.023")

FBI Conclusions

Mechanism of Failure

For uncommanded discharge, TWO safeties must fail:

1. Primary sear engagement lost
2. Striker safety lock rendered inoperable

Key Findings

• Uncommanded discharge is technically possible if sear engagement is lost
• Normal law enforcement movements can disable striker safety lock
• Issue affects both used and brand-new M18 pistols
• Problem successfully reproduced in controlled laboratory conditions

Safety Implications

• Striker safety lock is the "last line of defense"
• Movement and friction can disable this final safety mechanism
• Creates condition where uncommanded discharge is possible during normal law enforcement activities

FBI Recommendations

• Michigan State Police should weigh report findings with internal investigation
• Consider technical findings when determining M18 suitability as duty weapon
• Further exploration needed to fully assess potential risk

Report Significance

• Does NOT declare SIG Sauer negligent
• Provides objective technical documentation
• Confirms uncommanded discharge plausibility under real-world conditions
• Adds to existing scrutiny of M18/P320 platform safety concerns