In the olden days, soldiers killed when they fired a bullet at an enemy they could see. Then came indirect fire—lobbing mortars from afar, hoping for a lucky hit.

Now the Army is working on a new round, combining the best of both, by reducing the bad guy’s ability to hide.

Troops on the battlefield like to be “in defilade”—protected from enemy fire by physical obstacles. The Army’s new Small Arms Grenade Munition (SAGM) round is designed to remove the advantage offered by such cover: it explodes in midair after it has cleared whatever shield the enemy is hiding behind.

“It has a sensor that will sense defilade or walls or anything that somebody will be hiding behind,” SAGM chief Steven Gilbert says in a Pentagon release. “And basically detects it without the need of a laser range finder.” He has estimated the new round would more than double the lethality of existing grenade rounds at ranges of up to 500 meters.

Such a capability would have come in handy in the wars in Afghanistan and Iraq, where anti-U.S. forces routinely sought shelter in walled compounds. “Warfighter lacks ability to engage combatants in defilade,” a 2012 briefing slide grumbled. “Grenade overshoots the target.”

The new round would give U.S. troops “a higher probability of achieving a first-shot kill against enemy personnel,” Gilbert adds, and could “defeat personnel targets in defilade positions at increased ranges with greater accuracy and lethality.”

Army engineers have spent three years mating sensors to explosives to ensure the round explodes at a "sweet spot" designed to increase the chances of a kill. Chris Boston / U.S. Army

The Army’s Joint Service Small Arms Program, part of the service’s Armament Research, Development and Engineering Center (known to friends as JSSAP-ARDEC) at New Jersey’s Picatinny Arsenal, has been developing the thumb-shaped, four-inch round for the past three years.

It’s the ultimate fire-and-forget weapon: the soldier doesn’t need to do anything before firing, other than point it toward whatever obstacle the enemy is using for defensive cover. “All the soldier would need to do is aim the weapon and fire it,” Gilbert told the Army’s C. Todd Lopez. “He’d have to have good aim…or the round won’t detect the wall. You have to have some sort of accuracy.”

Among Pentagon wags, “close enough” has long been deemed good enough for nuclear weapons. It could also end up being good enough for the Small Arms Grenade Munition if a formal Pentagon evaluation, set to begin in July, pans out.

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