US M605 Combination Mine Fuze

Overview

The M605 Combination Mine Fuze is a dual-action mechanical fuze designed to initiate bounding fragmentation mines through either direct pressure or tripwire tension. As the standard fuze for the M16 series of anti-personnel mines, the M605 represents a critical component of American area denial systems developed during the Cold War era. Its distinctive three-pronged pressure head and integrated tripwire capability made it highly versatile for defensive minefield applications.

Country/Bloc of Origin

  • Country: United States of America
  • Developer: U.S. Army Ordnance Department
  • Period of Development: 1950s
  • First Fielded: Late 1950s, concurrent with M16 mine adoption
  • International Use: Exported to NATO allies and other nations receiving U.S. military aid; design influenced similar fuzes in Portugal (T253), Belgium, and other countries

Ordnance Class

  • Type: Mine fuze (combination pressure/tension)
  • Primary Role: Initiation device for bounding anti-personnel fragmentation mines
  • Secondary Capability: Can function as general-purpose firing device for booby traps when separated from mine body
  • Activation Method: Dual-mode (pressure or tripwire pull)
  • Delivery/Emplacement: Hand-emplaced with associated mine; screws into fuze well

Ordnance Family/Nomenclature

Official Designations:

  • Fuze, Mine, Combination: M605
  • NSN: 1390-00-700-1426 (complete assembly)

Associated Mines:

  • Mine, Antipersonnel: M16
  • Mine, Antipersonnel: M16A1
  • Mine, Antipersonnel: M16A2
  • Mine, Antipersonnel, Practice: M8, M8A1 (with practice variant M10/M10A1/M10A2)

Related Fuzes in U.S. Inventory:

  • M7, M7A1 – Earlier combination fuzes for M3 AP mine
  • M606 – Anti-tank mine fuze (non-metallic)
  • M607 – Anti-tank mine fuze
  • M2, M2A1, M6A1 – Earlier combination fuzes for M2 series mines

Practice Variant:

  • Fuze, Mine, Combination, Practice: M10, M10A1, M10A2

Hazards

Primary Hazards:

  • Mechanical Sensitivity: Pressure of 8-45 pounds (3.6-9 kg) on the prongs or pull of 3-15 pounds (1.4-4.5 kg) on the tripwire will initiate the device
  • Pyrotechnic Elements: Contains primer, delay charge, relay charge, and igniter charge capable of igniting propelling charge
  • Fragmentation Risk: When installed in mine, initiation results in bounding fragmentation with 27-30 meter casualty radius

Environmental Concerns:

  • Prolonged exposure to moisture may degrade pyrotechnic elements, potentially causing hangfires or misfires
  • Extreme temperatures can affect delay timing reliability
  • Corrosion of metal components may cause binding of safety pins or mechanical parts

UXO Considerations:

  • Failed or partially initiated M605 fuzes remain extremely hazardous
  • Tripwires may be difficult to detect and can remain tensioned for extended periods
  • Anti-handling devices may be attached to the mine body, creating secondary hazards during clearance
  • The three-pronged pressure head is highly susceptible to accidental activation during detection operations

Danger Areas:

  • When armed in M16 mine: 200-meter danger radius for clearance operations
  • Casualty radius upon detonation: 27 meters (M16/M16A1), 30 meters (M16A2)

Key Identification Features

Physical Dimensions:

  • Height (fuze alone): Approximately 4.5 inches (114 mm)
  • Diameter: Approximately 1.5 inches (38 mm) body
  • Weight: Less than 1 pound (included in mine weight of approximately 8 lbs)

Distinctive Features:

  • Three-Pronged Pressure Head: Most distinctive feature; three curved metal prongs extending upward from central post
  • Cylindrical Metal Body: Houses cocking mechanism, trigger pin, release pin, and firing pin assemblies
  • Release Pin Ring: Located on side of fuze body for tripwire attachment
  • Two Cotter Pin Safety Pins: One through release pin bearing against body; one through firing pin between prongs
  • Interlocking Pin: Additional safety device between the two safety pins
  • Hexagonal Fuze Well Interface: Threads into mine body; shipping plug present when packaged separately

Color and Markings:

  • Olive drab (OD) finish on metal components
  • Yellow markings indicate high explosive components
  • Nomenclature and lot number typically stamped on body

Materials:

  • Steel body and prongs
  • Brass or steel firing pin components
  • Pyrotechnic delay elements

Fuzing Mechanisms

Activation Modes:

Pressure Activation:

  • Pressure of 8-45 pounds (3.6-9 kg) applied to one or more prongs
  • Causes release of cocked firing pin through trigger pin mechanism

Tripwire (Tension) Activation:

  • Pull of 3-15 pounds (1.4-4.5 kg) on release pin ring
  • Withdraws release pin allowing firing pin to strike primer

Internal Components:

  • Cocking Mechanism: Pre-loads firing pin spring during manufacture
  • Trigger Pin: Engages under pressure application
  • Release Pin: Holds firing pin in cocked position; withdraws under tripwire tension
  • Firing Pin: Spring-loaded; strikes percussion cap upon release
  • Coil Springs: Fitted to trigger pin, release pin, and firing pin

Firing Train (Base Assembly):

  1. Percussion cap/primer – struck by firing pin
  2. Delay charge – provides time delay for victim to move off mine top
  3. Relay charge – transfers fire to igniter
  4. Igniter charge – initiates propelling charge in mine body

Safety Systems:

  • Safety Pin #1: Cotter pin through release pin; bears against body to prevent accidental pull
  • Safety Pin #2: Cotter pin through firing pin end, positioned between prongs to prevent depression
  • Interlocking Pin: Connects the two safety pins; must be removed before either safety can be withdrawn
  • Shipping Configuration: Both safety pins installed with pull strings attached

Arming Sequence:

  1. Install fuze in mine fuze well
  2. Attach tripwire to release pin ring (if using tension mode)
  3. Remove interlocking pin
  4. Remove safety pin from firing pin (between prongs)
  5. Remove safety pin from release pin (pull gently with fingers, not by string)

CAUTION: When arming, always pull the positive safety pin with fingers rather than the string to avoid imparting shock that could actuate the fuze.

History of Development and Use

Origins: The M605 fuze was developed as part of the M16 mine system, which itself was based on captured German S-mine (Schrapnellmine 35) documentation obtained during and after World War II. The German “Bouncing Betty” concept proved highly effective and was adopted by multiple nations in the postwar period.

Development Timeline:

  • 1930s: German development of S-mine and associated S.Mi.Z.35 fuze
  • 1944-1945: U.S. forces encounter S-mines extensively in North African, Italian, and European theaters
  • Late 1940s: U.S. Army Ordnance begins development of American bounding mine based on S-mine principles
  • 1950s: M16 mine and M605 fuze developed and standardized
  • 1957: Technical documentation published (TM for M16 with M605)
  • 1960s-1970s: M16A1 and M16A2 variants introduced with compatible M605 fuze

Combat Employment:

  • Vietnam War: Extensive use in defensive perimeters, ambush positions, and area denial
  • Cold War Europe: Stockpiled for potential Warsaw Pact invasion scenarios
  • Middle East: Exported to allied nations; encountered in various regional conflicts

Current Status:

  • The United States is a signatory to the Ottawa Treaty (1997) banning anti-personnel mines
  • U.S. military stocks of M16 mines largely destroyed or demilitarized
  • M605 fuzes may still exist in stockpiles of nations not party to the Ottawa Treaty
  • Significant UXO concerns remain in former conflict zones

Production:

  • Manufactured by various U.S. defense contractors
  • Production quantities classified but numbered in the hundreds of thousands
  • Fuzes issued both installed in mines and as separate supply items

Technical Specifications

SpecificationValue
Fuze TypeCombination (pressure/tension)
Pressure Activation8-45 lbs (3.6-9 kg)
Tripwire Activation3-15 lbs (1.4-4.5 kg)
Delay TimeShort pyrotechnic delay (allows victim to move off mine)
Operating Temperature-40°F to +125°F (-40°C to +52°C) typical military range
Safeties2 cotter pins plus interlocking pin
Compatible MinesM16, M16A1, M16A2
Practice VariantM10, M10A1, M10A2
MaterialSteel, brass, pyrotechnic compounds

Mine System Performance (when installed in M16A2):

  • Bounding height: Approximately 2 meters (6.5 feet)
  • Casualty radius: 30 meters
  • Projectile weight: 3.5 kg
  • Total mine weight (fuzed): Approximately 8 lbs (3.6 kg)

Frequently Asked Questions

Q: Why is the M605 called a “combination” fuze? A: The M605 is designated a combination fuze because it incorporates two distinct activation methods in a single device: pressure (via the three-pronged head) and tension/pull (via the side-mounted release pin ring). This dual capability allows tactical flexibility in employment—the mine can be configured for direct-pressure activation when buried flush with the ground, tripwire activation across likely avenues of approach, or both simultaneously for maximum coverage.

Q: How does the M605 differ from earlier U.S. combination fuzes like the M7A1? A: The M605 represents an evolutionary improvement over the M7A1 fuze used with the M3 antipersonnel mine. Key differences include a more robust cocking mechanism, improved waterproofing, refined pressure sensitivity ranges, and the addition of the interlocking safety pin between the two primary safeties. The M605 also features enhanced delay charge reliability to ensure consistent bounding performance of the M16 mine projectile.

Q: What is the purpose of the delay element in the M605 firing train? A: The pyrotechnic delay in the M605 base assembly serves a critical tactical function. When the fuze is activated, the delay allows the victim approximately 0.5-1 second to step off or move past the mine before the propelling charge fires. This ensures the mine body can launch vertically unobstructed, reaching its optimal detonation height of approximately 2 meters for maximum fragmentation effect against standing personnel.

Q: Can the M605 fuze be used separately from the M16 mine? A: While designed specifically for the M16 series mines, the M605 can technically function as a general-purpose firing device for booby trap applications. However, this is not its intended use and presents significant safety concerns. The base assembly contains pyrotechnic delay elements rather than an instantaneous detonator, making it unsuitable for direct demolition applications. Purpose-built firing devices like the M1, M3, or M5 are preferred for non-mine applications.

Q: Why must the safety pins be removed in a specific order? A: The arming sequence is designed to provide maximum safety during emplacement. The interlocking pin must be removed first as it physically prevents removal of either primary safety. The firing pin safety (between the prongs) is removed second to allow the pressure mechanism to function, but the release pin safety still prevents accidental tripwire activation. Only after the tripwire is properly installed and tensioned is the final safety removed. This sequence ensures the mine cannot be inadvertently activated during the vulnerable emplacement period.

Q: What makes the M16/M605 system particularly dangerous for demining operations? A: Several factors combine to make this system exceptionally hazardous. The three-pronged pressure head can be activated by the movement of a metal detector head across the ground surface. The low tripwire activation force (as little as 3 pounds) means wires can be triggered by slight contact. Anti-handling devices are often attached to the mine body, creating secondary hazards. The bounding mechanism means the mine projects upward to torso height before detonating, increasing lethality. Finally, the extended danger radius of 200 meters requires large standoff distances during any render-safe procedure.

Q: How can you distinguish a live M605 from the practice M10 variant? A: The practice M10/M10A1/M10A2 fuzes are visually similar but have several distinguishing features. Practice fuzes typically have blue markings or components indicating their training status. The base assembly of a practice fuze contains a small smoke or noise-producing charge rather than the full pyrotechnic train of a live fuze. Additionally, practice fuzes may be marked “PRACTICE” or “INERT” on the body. When in doubt, all fuzes should be treated as live until verified by qualified EOD personnel.

Q: What countries have produced copies or derivatives of the M605 fuze? A: The M605 design influenced several international variants. Portugal developed the T253 fuze for their M432 bounding mine, which is functionally similar. Belgium produced comparable fuzes for their NR 442 mine. Various nations receiving U.S. military aid received M16 mines with M605 fuzes, and some may have produced unauthorized copies. The basic three-pronged combination fuze concept has become a standard pattern for bounding mines worldwide, though specific mechanisms vary.

Safety Notice

All ordnance items should be considered dangerous until proven safe by qualified Explosive Ordnance Disposal (EOD) personnel. The M605 fuze and associated M16 mines remain lethal decades after emplacement. Never attempt to handle, disarm, or move suspected ordnance. Mark the location, evacuate the area, and report findings to military or law enforcement authorities immediately.

This information is provided for educational and identification training purposes only.