Introduction
The MK II fragmentation hand grenade, commonly known as the “pineapple” grenade, is one of the most iconic pieces of military ordnance in history. Introduced by the United States in 1918, this grenade has played a significant role in numerous conflicts throughout the 20th century, including both World Wars, the Korean War, and the Vietnam War.
Functioning of the MK II Grenade
The MK II grenade operates through a simple yet effective mechanism. It features a fragmentation body attached to a percussion-cap-and-time-fuse-delay detonation system. The grenade’s body is made of cast iron and is characterized by its distinctive pattern of protruding blocks, which aid in handling and fragmentation. The safety pin, held in place by a ring, must be removed to arm the grenade. Once the safety lever (spoon) is released, the striker hits the percussion cap, igniting a chemical delay fuse that burns for approximately five seconds before detonating the main charge.
The explosive charge inside the MK II typically consists of about two ounces of TNT. When detonated, the explosion shatters the iron body into numerous high-velocity fragments, creating a lethal radius of about 30 yards. The primary purpose of this fragmentation is to incapacitate enemy personnel within its effective range.
Manufacturing Process
The manufacturing of the MK II grenade involved several key stages, reflecting the technological and industrial capabilities of the early 20th century. The grenade’s body was cast from iron and initially filled with low explosive compounds like EC powder. However, later versions used high explosives such as TNT, nitrostarch, or a 50/50 amatol mix. The grenade bodies were often painted gray or black to prevent rust, while practice grenades were painted red or blue to distinguish them from live munitions.
Production variants of the MK II included the Mk II, Mk IIA1, and various practice models. Each version saw improvements in fuse design and filling methods. For example, the Mk IIA1 variant, introduced in 1942, eliminated the bottom filler hole and used the more reliable M10A2 igniting fuse. These advancements ensured greater safety and reliability in the field.
Historic Use and Evolution
The MK II grenade was first deployed during the latter months of World War I, replacing the problematic MK I grenade. Its robust design and effectiveness quickly made it a staple in the U.S. military’s arsenal. During World War II, the MK II was widely used by American forces and was even adapted for use with rifle-mounted grenade launchers, enhancing its tactical versatility.
The MK II continued to serve in the Korean War and saw extensive use during the Vietnam War. Its rugged design and reliable performance made it a favorite among soldiers. However, by the 1950s, advancements in grenade technology led to the development of the M26 “lemon” grenade, which gradually replaced the MK II in U.S. military service. The M26 featured a more aerodynamic shape and a fragmentation coil, which provided more consistent fragmentation patterns.
Despite being phased out of active service, the MK II remains a symbol of mid-20th-century military ingenuity. Its design influenced many subsequent grenade models used worldwide, and it continues to be a collectible item among military enthusiasts.
Conclusion
The MK II fragmentation hand grenade stands as a testament to the evolution of military technology. From its inception in 1918 to its widespread use in multiple conflicts, the MK II’s impact on modern warfare is undeniable. Its simple yet effective design ensured that it remained a reliable tool for soldiers for several decades. Today, it remains an iconic piece of military history, symbolizing the ingenuity and adaptability of early 20th-century ordnance design.