Mk 2 grenade

Mk 2 Grenade
World War II-era Mk 2 grenade
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

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 grenade 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, 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.