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M61 Fragmentation Grenade (Vietnam)

M61 Frag After WWII, efforts were under way to improve upon the cast iron Mk.II design. The problem with a grenade that produces limited heavy fragments is consistency of coverage. Many times, even close to the point of detonation, grenades would not be effective. On the other hand, heavy fragments can have lethal effect, far beyond the intended target area. Experience showed that hand grenades needed to be more effective close in, and long range hazards needed to be minimized.

Towards that end, a new class of grenade was developed. A high yield limited range fragmentation grenade.

The first of this type was the M26, developed prior to the Korean War. The M61 is an improved version of that.  It has a light sheet metal body, with an internal fragmentation coil, producing a limited but effective casualty radius (15 meters).

M204A2 Fuze w/Jungle Clip
The Jungle Clip

The M61 incorporates a secondary safety feature called the Jungle Clip.

While never a design intent, grenade safety levers have long been used as a convenient carry hook, clipped over web gear. Experience in Vietnam showed that jungle growth had an unfortunate tendency to snag hand grenade safety pins. The jungle clip is a secondary back-up safety device, used to clamp the lever to the grenade in the event that the pin is accidentally pulled.

Shown here is the first model. A simple add-on wire part. When unhooked it remains attached to the grenade.

The grenade now required two separate arming actions, pulling the pin, and releasing the jungle clip, prior to throwing the grenade.

M61 Sectional View M61 Frag Coil

At left is a sectional view of the interior of the M61. You can see the internal fragmentation coil. Nested around the detonator are tetryl booster elements, which assisted detonation.
The M204 fuze delay is completely contained, resulting in an almost silent fuze which didn't emit sparks or smoke, a big improvement over earlier WWII designs.

Above is a bottom view, looking inside the grenade body.