The XM-25

An article on the deployment and use of the XM-25:

The XM25, as the new gun is known, weighs about 6kg (13lb) and fires a 25mm round. The trick is that instead of having to be aimed directly at the target, this round need only be aimed at a place in proximity to it. Once there, it explodes—just like Shrapnel’s original artillery shells—and the fragments kill the enemy. It knows when to explode because of a timed fuse. ...

A handful of XM25s are now being tested in Afghanistan by the Americans. So far, they have been used on more than 200 occasions. Most of these fights ended quickly, and in America’s favour, according to Lieutenant-Colonel Shawn Lucas, who is in charge of the weapon’s field-testing programme. Indeed, the programme has been so successful that the army has ordered 36 more of the new rifles.

Each rifle bullet is programmed, before it is fired, by a second computer in the rifle itself. To determine the distance to the target, the gunman shines a laser rangefinder attached to the rifle at whatever is shielding the enemy. If that enemy is in a ditch, a nearby object—a tree trunk behind or to the side of the ditch, perhaps—will do. Looking through the rifle’s telescopic sight, the gunman then estimates the distance from this object to the target. He presses a button near the trigger to add that value to (or subtract it from) the distance determined by the rangefinder.

When the round is fired, the internal computer counts the number of rotations it makes, to calculate the distance flown. The rifle’s muzzle velocity is 210 metres a second, which is the starting point for the calculation. When the computer calculates that the round has flown the requisite distance, it issues the instruction to detonate. The explosion creates a burst of shrapnel that is lethal within a radius of several metres (exact details are classified). And the whole process takes less than five seconds.

Just how the turn-counting fuse works is an even more closely guarded secret than the lethal radius—though judging by the number of failed attempts to hack into computers that might be expected to hold information about it, many people would dearly like to know. Certainly, the trick is not easy. An alternative design developed in South Korea, which clocks flight time rather than number of rotations, seems plagued by problems. ...

The XM25, in contrast, appears to work well. It is accurate at ranges of up to 500 metres. That is almost as far as America’s main assault rifle, the M-16, can shoot conventional bullets with accuracy. More pertinently, it is nearly double the range of the AK-47, a rifle of Soviet design that is used by many insurgent groups. And according to Sergeant-Major Bernard McPherson, part of the XM25’s development programme in Virginia, it is receiving rave reviews from soldiers in the field.

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None of this is cheap. An XM25 with a thermal sight and a four-round magazine is reckoned by informed observers of the field to cost about $35,000. The bullets, which have to be made by hand at the moment, clock in at several hundred dollars each. But the price of a bullet could fall to as low as $25 when ATK switches to automated production. And even at its current price, both gun and ammunition compare favourably with alternative methods of dealing with dug-in gunmen.

The most reliable of these is an airstrike. But that is costly. Grenade launchers, mortars and conventional artillery are cheaper, but more likely than a single explosive bullet to cause collateral damage.