US M213 Grenade Fuze

Overview

The M213 Grenade Fuze is a pyrotechnic delay fuze designed for use with U.S. military hand grenades. It serves as the primary ignition and delay mechanism for the M67 fragmentation grenade and several other grenades in the U.S. inventory. The M213 is characterized by its reliable delay function, safety features, and distinctive spoon-and-pin configuration that has become iconic in modern grenade design. This fuze represents an evolution of earlier U.S. grenade fuze designs, incorporating improved safety mechanisms and more consistent delay timing.

Country/Bloc of Origin

  • Country: United States of America
  • Developer: U.S. Army Armament Research, Development and Engineering Center (ARDEC)
  • Time Period: Developed in the 1960s alongside the M67 fragmentation grenade
  • Military Bloc: NATO
  • International Production: Licensed production in various NATO and allied nations including South Korea, Israel, and several European countries

Ordnance Class

  • Type: Pyrotechnic delay grenade fuze
  • Primary Role: Initiation device for hand-thrown fragmentation and offensive grenades
  • Delivery Method: Hand-emplaced via manual throwing
  • Category: Small arms ammunition component / grenade fuze assembly

Ordnance Family/Nomenclature

Official Designations:

  • M213 Fuze (primary designation)
  • Fuze, Hand Grenade, M213

Related Variants:

  • M213A1: Improved version with enhanced moisture resistance
  • M228: Practice fuze variant for training grenades
  • M217: Electronic fuze replacement (limited adoption)

Predecessor Fuzes:

  • M204: Earlier generation fuze used with M26 series grenades
  • M205A1/A2: Detonating fuzes for practice grenades

Compatible Grenades:

  • M67 Fragmentation Grenade
  • M68 Practice Grenade (inert)
  • M69 Practice Grenade
  • MK3A2 Offensive Grenade (concussion)

NSN: 1330-00-056-3976 (M213)

Hazards

Primary Hazards:

  • Pyrotechnic ignition: The fuze contains a primer and delay element that produce hot gases and flame
  • Initiation of main charge: When functioning correctly, the fuze will detonate the grenade’s explosive fill

Sensitivity Factors:

  • Impact sensitive: The striker mechanism can be released if the safety lever is not properly restrained
  • Pin removal hazard: Once the safety pin is removed, only the safety lever (spoon) prevents striker release
  • Heat sensitivity: Extended exposure to high temperatures can degrade the delay element, causing unpredictable timing

Environmental Considerations:

  • Moisture infiltration can cause fuze failure or erratic delay times
  • Extreme cold may slow the delay element burn rate
  • Corrosion of the striker spring can lead to weak strikes and misfires

UXO Considerations:

  • A grenade with the pin removed and spoon missing that has not detonated should be considered extremely dangerous
  • Fuze malfunctions can result in “duds” that may function if disturbed
  • Never attempt to reinsert a safety pin once it has been removed
  • Aged fuzes may have degraded delay elements resulting in instantaneous or delayed function beyond normal parameters

Kill Radius (when attached to M67):

  • Lethal radius: 5 meters (16 feet)
  • Casualty radius: 15 meters (49 feet)
  • Fragmentation hazard radius: 230 meters (755 feet)

Key Identification Features

Physical Dimensions:

  • Overall length: Approximately 63 mm (2.5 inches)
  • Body diameter: Approximately 25 mm (1.0 inch)
  • Weight: Approximately 28 grams (1 oz)

External Features:

  • Safety lever (spoon): Curved, flat metal lever approximately 76 mm (3 inches) long, olive drab or unpainted metal
  • Safety pin: Cotter-pin style with pull ring, typically bright metal or olive drab
  • Fuze body: Cylindrical, threaded aluminum or zinc alloy housing
  • Striker assembly: Concealed within fuze body, held under spring tension

Color and Markings:

  • Fuze body: Olive drab (OD) green
  • Markings stamped or printed on body include:
    • “FUZE M213” or “M213A1”
    • Lot number
    • Manufacturer code
    • Date of manufacture
  • Safety clip (if present): Bright yellow or unpainted metal

Material Composition:

  • Body: Die-cast zinc alloy or aluminum
  • Safety lever: Sheet steel, phosphate coated
  • Striker: Hardened steel
  • Delay element housing: Brass or copper

Fuzing Mechanisms

Operating Principle: The M213 is a percussion-initiated, pyrotechnic delay fuze that functions through the following sequence:

Arming Sequence:

  1. Safety pin removal: The user pulls the safety pin while maintaining grip on the safety lever
  2. Lever release: Upon throwing, the user releases the safety lever
  3. Striker release: The spring-loaded striker rotates and impacts the primer
  4. Primer ignition: The percussion primer fires, igniting the delay element
  5. Delay burn: The pyrotechnic delay column burns for 4-5 seconds
  6. Detonator function: The delay element fires the detonator
  7. Main charge initiation: The detonator initiates the grenade’s explosive fill

Safety Mechanisms:

  • Safety pin: Primary safety device preventing striker release
  • Safety lever: Secondary safety maintaining striker position after pin removal
  • Safety clip: Optional tertiary safety device used during transport (bright yellow clip over lever)

Delay Timing:

  • Nominal delay: 4.0 to 5.5 seconds
  • This delay allows the thrower to reach cover before detonation

Detonator Type:

  • The M213 uses an integral detonator containing a small quantity of lead azide and RDX

History of Development and Use

Development Background: The M213 fuze was developed in the early 1960s as part of the U.S. Army’s modernization of infantry weapons. It was designed to replace the M204 fuze series and provide improved reliability, safety, and manufacturing economy. The development coincided with the introduction of the M67 fragmentation grenade, which replaced the earlier M26 and M61 grenades.

Design Philosophy: The M213 incorporated lessons learned from World War II and the Korean War, where grenade fuze failures and unpredictable delay times had caused friendly casualties. Key improvements included:

  • More consistent delay timing
  • Improved moisture resistance
  • Better striker spring reliability
  • Simplified manufacturing processes

Combat Deployment:

  • Vietnam War (1965-1975): First large-scale combat use; the M213/M67 combination proved highly effective in jungle warfare
  • Grenada (1983): Used during Operation Urgent Fury
  • Panama (1989): Employed in Operation Just Cause
  • Gulf War (1990-1991): Standard issue during Desert Shield/Desert Storm
  • Global War on Terror (2001-present): Continues in service in Afghanistan, Iraq, and other theaters

Current Status:

  • Remains in active service with U.S. Armed Forces
  • Standard fuze for M67 fragmentation grenades
  • Widely exported to U.S. allies and partners
  • No planned replacement in the near term

Production:

  • Millions produced since the 1960s
  • Multiple manufacturers including:
    • Day & Zimmermann
    • American Ordnance
    • Various international licensees

Technical Specifications

SpecificationValue
Fuze TypePyrotechnic delay, percussion-initiated
Delay Time4.0 – 5.5 seconds
Overall Length63 mm (2.5 in)
Body Diameter25 mm (1.0 in)
Weight28 g (1.0 oz)
Thread Size7/16-28 UNEF
Primer TypePercussion, stab-initiated
Delay ElementGasless delay composition
DetonatorLead azide / RDX
Operating Temperature-40°C to +52°C (-40°F to +125°F)
Storage Life10+ years under proper conditions
Safety DevicesSafety pin, safety lever, optional safety clip

Frequently Asked Questions

Q: Why does the M213 fuze have a delay rather than detonating on impact? A: The 4-5 second delay serves multiple critical purposes. It allows the thrower time to take cover after releasing the grenade, prevents the enemy from throwing the grenade back (though this is still possible with quick reactions), and ensures the grenade detonates at an optimal height or location rather than potentially burying itself in soft ground where fragmentation would be reduced. The delay timing represents a calculated balance between these tactical considerations.

Q: What happens if the safety pin is bent or difficult to remove? A: A bent or corroded safety pin indicates potential damage or degradation to the fuze. In training environments, such grenades should be set aside for inspection. In combat, soldiers are trained that excessive force to remove a pin could indicate a problem, and the grenade should be used with extra caution. The pin is designed to require approximately 10-35 pounds of pull force; significantly more suggests corrosion or damage.

Q: How does the M213 differ from the Soviet UZRGM fuze? A: While both are pyrotechnic delay grenade fuzes, they have significant design differences. The M213 uses a rotating striker that pivots when the spoon is released, while the UZRGM uses a linear striker that travels straight down. The M213 typically has a slightly shorter delay (4-5 seconds vs. 3.2-4.2 seconds for UZRGM). The threading and dimensions differ, making them incompatible with each other’s grenades. The M213’s safety lever is generally longer and curves more dramatically than the UZRGM’s.

Q: Can a grenade with a released spoon be rendered safe? A: No. Once the safety lever has been released, the striker has already impacted the primer and the delay element is burning. There is no way to stop this process. The only safe action is to throw the grenade to a safe location immediately. Attempting to hold or “cook off” a grenade is extremely dangerous, as delay times can vary and the grenade may detonate sooner than expected.

Q: What causes the fuze to fail and create a “dud” grenade? A: Fuze failures can result from several factors: moisture contamination of the delay element or primer, corrosion of the striker or spring mechanism, manufacturing defects, improper storage conditions, physical damage to the fuze body, or extreme age degradation. A dud grenade should never be considered safe, as it may detonate if disturbed—the delay element may still be smoldering or the detonator may be sensitized.

Q: Why is the safety lever called a “spoon”? A: The term “spoon” is informal military slang that has been used since at least World War II. It refers to the shape of the safety lever, which somewhat resembles a spoon’s handle. The official military terminology is “safety lever,” but “spoon” remains widely used in training and tactical communications due to its brevity and universal recognition among military personnel.

Q: How do EOD technicians handle grenades with missing pins but intact spoons? A: This scenario requires extreme caution. EOD procedures typically involve establishing a cordon, using remote handling tools when possible, and never trusting that the spoon will remain in place. Even slight movement could release the spoon and initiate the fuze. If the grenade must be moved, specialized equipment is used, and personnel maintain maximum distance. In many cases, in-place destruction is the safest option.

Q: What is the purpose of the yellow safety clip sometimes seen on M213-fuzed grenades? A: The safety clip is an additional transport safety device that physically prevents the safety lever from moving even if the pin is accidentally pulled. It’s typically used during shipping and storage. Before a grenade is issued for combat or training use, the safety clip is removed. The bright yellow color ensures high visibility so the clip isn’t overlooked before use.

SAFETY NOTICE: This lesson is intended for educational and training purposes. All ordnance should be considered dangerous until proven safe by qualified personnel. Unexploded ordnance should never be handled by untrained individuals—report findings to military or law enforcement authorities.