Hand grenade activation indicator

Prevents the arming lever from returning to its original position and falsely indicating that the fuze is not burning

Military Technology

An expert in hand grenades at the U.S. Army’s Picatinny Arsenal has invented a novel safety feature that indicates a burning fuse.

Drill instructors and range cadre know that some military recruits (or conscripts in foreign armies) will become nervous holding a hand grenade and freeze after removing the safety pin, which requires an instructor to carefully take the grenade into their own hand and throw down range. For safety reasons, attempting to reinsert a grenade’s safety pin is discouraged by the U.S. military.

Instructors also carefully educate recruits not to “milk” a grenade after removing the safety pin. Milking, relaxing and squeezing the throwing hand while it is maintaining the grenade’s arming lever, also known as the spoon, can cause an inadvertent activation of the grenade fuse. With the spoon appearing to still be in the safe position but the fuse burning, a recruit may unknowingly hold a grenade until detonation.

The U.S. military primarily uses the M67 hand grenade, which has a 4.0-5.6 second delay fuze. It is designed to produce mass casualties through high-velocity fragmentation. While dropped grenades can be kicked into trenches or moved away from, instructors have less chance of protecting recruits and themselves from a milked grenade. The risk is also very real for more experienced soldiers. According to a 2008 Army publication, one soldier was killed because he milked an M67 during a live-fire training exercise; three other soldiers were wounded.

Richard Lauch, a retired Marine now an engineer at the Picatinny Arsenal, has invented a modification to the fuze assembly that acts as an explosive train initiation indicator in hopes of preventing accidental detonations.

It allows the warfighter to quickly and reliably determine striker activation and grenade initiation, without the need for close inspection. If the spoon travels far enough to activate the fuse, the device physically blocks the spoon from being returned to its initial, safe position. See the attached patent below for detailed drawings.

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