Mk 2 grenade

The Mk 2 grenade (sometimes written Mk II) is a fragmentation type anti-personnel hand grenade introduced by the U.S. armed forces in 1918. It was the standard issue anti-personnel grenade used during World War II and in later conflicts, including the Vietnam War. Replacing the failed Mk I of 1917, it was standardized in 1920 as the Mk II, and redesignated the Mk 2 in 1945.

The Mk 2 was replaced by the M26-series (M26/M61/M57) and later M33 series (M33/M67). It was phased out gradually in service beginning with the Korean War. Due to the tremendous quantity manufactured during World War 2, it was in limited standard issue with the US Army and US Marine Corps throughout the 1950s and 1960s. The U.S. Navy was one of the last users when it was discontinued in 1969.

The Mk II was manufactured with grooves in the cast iron to enhance fragmentation and provide a better grip handling and throwing the grenade. These gave it the appearance of a pineapple and origin of that nickname. It was also commonly referred to as a "frag" grenade, in contrast to the Mk 3 concussion grenade.

The original Mk II grenade had a 3/8-inch threaded plug in its base covering the opening used to place the explosive filling. The improved "Mk IIA1" (a designation used informally by armorers, historians, and collectors but was never officially by the US military) introduced in 1942 was filled through the fuse well instead.

Low explosive Mk II grenades were filled with smokeless EC powder powder, which produced an adequate amount of fragmentation and did away with the need of a detonator. It was initially replaced by a small length of safety fuse terminated with a black powder igniter charge. Production grenades with the EC powder filler used the M10 series of igniting fuse.

High Explosive Mk II's used flaked or granular TNT. Pre-war Mk IIs with a TNT filler were identified with an all-yellow body as a warning to users. Wartime grenades were repainted olive drab for camouflage purposes with a narrow yellow band below the fuse. Repainted grenades usually lacked the yellow band.

The Mk II used the M5, M6, and M10 series fuses. These early fuses made a loud "bang" and produced sparks when activated. They had other problems as well. The M10-series' powder train made a "hissing" sound as it burned, potentially alerting the enemy of its presence. The M5 and M6 series sometimes prematurely detonated when the flash from the primer hit the TNT charge rather than the delay fuse. Moisture could get in under the foil fuse cap, causing the weapon to fail to detonate. Improved smokeless and (almost) silent fuses (like the M204-series) were later fitted after World War II.

Country Name Origin Year
United States of America 1918
Country Name Operational Year Retirement Year
United States of America 1918 View
Type Time-fused grenade
Place of origin United States
Service history
In service 1918–1960s
Used by Argentina
Brazil
Chile
Israel
Italy
Netherlands
Turkey
Philippines
United States
Wars World War I
World War II
Korean War
Vietnam War
Suez Crisis
Six Day War
Production history
Designer John Browning
Designed 1918
Specifications
Weight 1 lb 5 oz [595 grams]
Length 3 5/6" [111mm]
 length 2 5/16" [59mm]
Filling TNT or EC blank fire powder
Filling weight 2 oz
Detonation
mechanism
percussion cap & time fuse: 5 second delay


Specifications

  • Body: Made of cast iron with a grooved surface that is divided into 40 knobbed segments in 5 rows of 8 columns. Models made from 1918 to 1942 have a 3/4"-threaded baseplug to insert or remove the explosive filler. Models made from 1942 onwards were filled through the fuse well to speed up production.
  • Fuse: Dependent on variant, includes M5 and M6 detonating fuses (for Mk 2s with a High Explosive filler), and M10 igniting fuses (for Mk 2s with an EC Black Powder filler). The delay time was 4 to 5 seconds.
  • Charge: Either a Low Explosive (EC powder) or High Explosive (flaked or granular TNT) filler.
  • Markings: Low Explosive grenades were made of blackened iron or were painted Gray or Black to prevent rust. Pre-war High Explosive grenades were painted Yellow; wartime grenades (c.1942 and onward) were over-painted or painted Olive Drab with a Yellow ring at the top. Mk II Practice grenades (c.1920-1945) were painted Red (a practice copied from the French military). M21 Practice grenades (c.1945 to 1950s) were painted light Blue (a practice copied from the British military) and had blue-painted fuse levers, often with the end painted light brown indicating a "low explosive" marking charge.

End notes