U.S. SOCOM (Special Operations Command) appears to be the main customer for a new dual purpose (non-lethal/lethal) grenade design being developed by U.S. Army researchers. The ET-MP (Enhanced Tactical Multi-Purpose) grenade is meant to reduce the number of grenades that have to be carried in combat. Weight reduction for the infantry in combat has been a major gripe by the troops for a long time. It became worse since the late 1990s because much more effective (and heavier) protective vests were issued. Then came all the electronics.
With the flip of a switch the user can select lethal or non-lethal effect and also different fuze settings (how many seconds after it is thrown that it will explode.) ET-MP will also be easier to use left-handed. All this requires some new tech and lots of testing. The army does not expect to have the ET-MP ready for testing until 2020 and then there is the problem of cost. Thus the need to pay attention to SOCOM needs because if ET-MP is a lot more expensive than planned (a rather common outcome) only SOCOM could afford the new grenade.
SOCOM operators often fight in close proximity to the enemy and often with civilians (sometimes hostages being rescued) and is always looking for new “less lethal” grenades. An example of this occurred in 2013 when U.S. SOCOM ordered $40 million worth of the new SOHG (scalable offensive hand grenade) developed by a Finnish firm (Nammo). This was important for Nammo, because the only other customers it could find was the Finnish Armed forces and a few police agencies.
SOHG was more expensive than the standard offensive (no fragments) hand grenade and even the U.S. Army, which tried out the SOHG, has not been willing place a large order. An offensive grenade relies on blast, not fragments, to kill or injure the enemy. Often called concussion grenades they were developed to handle close (like door to door or in tunnels or trenches) where the enemy is so close that your fragmentation grenade will still produce fragments moving fast enough to hurt friendly troops nearby. Scalable refers to grenades that can have different amounts of their explosives removed by the user to produce different results. With one increment the grenade is basically a “flash-bang” that is meant to disorient (with a loud noise and bright flash) people, not really kill or injure. By adding 1 or 2 additional “increments” of explosives the user makes the grenade effective over a wider area and potentially lethal. These scalable grenades depend on explosives to injure, not fragments. They are also a lot more expensive, but for SOCOM operators the additional flexibility is often the difference between success and failure in an operation.
Offensive hand grenades have been around since World War I when they were invented for troops fighting in close quarters (enemy trenches). It was found that these grenades were also useful inside buildings and caves. Thus the original American Mk3 offensive grenade kept getting upgraded and was the basis of the SOHG and other new less lethal grenade designs. The Mk3A2 was made of waterproofed fiberboard with minimal metal components. The Mk3A2 weighs 440 gr (15.4 ounces), has a five second fuze, and contains 228 gr (8 ounces) of TNT. It was largely replaced in the 1990s by the M84. This was a more modern and less lethal (stun or “flash bang”) design invented for British SAS commandos in the 1960s. These weapons do not use explosives but rather have a fire and shatter proof body with perforations for momentary bright light and a very loud noise to escape. The effect is most intense 1-2 meters (up to 6 feet) from the detonation. M84 stun grenade weighs 236 gr (8.2 ounces), uses a 4.5 gr (.16 ounce) magnesium/ammonium nitrate mixture, and a 1-2.3 second fuze to generate up to 180 db of sound and 6-8 million Candela of light for up to 1.5 meters (5 feet away).
SOCOM has long led the way in developing more effective (but more expensive) weapons. This when 2001 came around SOCOM already had a new mini-grenade for close range combat. The 183 gr (6.4 ounce) HG-86 was half the size of the standard M67 fragmentation grenade. It had less destructive blast effect, but still put out some 1600 fragments (each about 2-3mm in size), the HG-86 got the job done with less damage to friendly troops who tossed it (usually right outside the room the grenade goes off in.) Another obvious advantage of this grenade is that you can carry more of them.
A lot of these new designs do not work out. The ET-MP is called a high-risk design because in combat even simple technology can be accidentally used the wrong way. Thus many combat troops consider the ET-MP a likely source of more friendly fire casualties. Even SOCOM operators prefer separate lethal (fragmentation) and less-lethal (stun) designs. Not just different in effect but different in shape so that in the dark, or because of the stress of combat, the user can easily tell by touch which grenade is which.