The XM-25 was originally one of two weapons (the other being a 5.56mm rifle) incorporated in the 18 pound XM-29 OICW. The OICW was developed, in the 1990s, as a replacement for the 40mm grenade launcher. The 40mm rounds weigh 19 ounces each, the 20mm OICW round weighs half that. But there were several major problems with the OICW. It was too heavy and ungainly, and the 20mm "smart shell" it fired did not appear capable of effectively putting enemy troops out of action. So, in August, 2003, it was decided to take the 5.56mm portion of the OICW and develop it as a separate weapon (the XM-8) and develop the grenade launcher part that fired the "smart shell" as the XM-25. But the XM-25 would use a 25mm shell, which would generate 50 percent more fragments (and heavier ones at that) than the 20mm shell of the OICW. The XM25 is expected to reach the troops by 2008. But that might happen sooner if the field testing continues to go well.
The 20mm and 25mm "smart shells" use a computer controlled fuze. The X M-25 operator can select four different firing modes via a selector switch on the weapon. The four modes include "Bursting" (airburst). For this to work, the soldier first finds the target via the weapons sighting system. The sight includes a laser range finder and the ability to select and adjust the range shown in the sight picture. For an air burst, the soldier aims at an enemy position and fires a round. The shell is optimized to spray incapacitating (wounding or killing) fragments in a roughly six meter radius. Thus if enemy troops are seen moving near trees or buildings at a long distance (over 500 meters), the weapon has a good chance of getting them with one shot. M-16s are not very accurate at that range, and the enemy troops will dive for cover as soon as M-16 bullets hit around them. With smart shells, you get one (or a few) accurate shots and the element of surprise.
The other modes are "PD" (point detonation, where the round explodes on contact), PDD (point detonation delay, where the round detonates immediately after it has gone through a door, window or thin wall) and "Window", which is used for firing at enemy troops in a trench, behind a stone wall or inside a room. The round detonates just beyond the aiming point. For buildings, this would be a window or door frame, cave entrance or the corner of a building (to get enemy troops thought to be around the corner.)
The XM25 is still a heavy weapon, with the final version coming in at nearly 18 pounds. The 25mm shells weigh over half a pound each. On the plus side, there is already a 25mm armor piercing round (using a shaped charge capable of penetrating over 50mm of armor) available. This makes the X M-25 capable of knocking out light armored vehicles. The U.S. Army has fired over 30 million 25mm shells from the cannon on its M-2 Bradley armored vehicles and was satisfied with the lethality of that shell against infantry. One of the new options with the XM-25 25mm round is a fuel-air explosive (or "thermobaric"). Such a shell would cause greater blast effect in an enclosed space, and actually suck most of the oxygen out of a cave or closed room long enough to make surviving troops at least a bit groggy. This gives the attacking troops an opportunity to rush in and kill the enemy, or take prisoners. In combat, every little advantage helps.
The XM-25 grenade launcher, which began field testing last May, is now being tested by American troops in Germany as well. So far, the troops have been very enthusiastic about the new weapon. Those who have served in Iraq, say the XM-25 would come in very handy there, because enemy gunmen often duck behind cars or other obstacles, and the XM-25 was designed to quickly get at people behind that kind of cover using computer controlled 25mm projectiles.