Weapons: Smart Grenades That Work Most Of The Time


March 19, 2013: The U.S. Army has halted use of its new XM25 computerized grenade launchers in Afghanistan, after a second one suffered a jam and an explosion (on February 2nd) that injured the user and heavily damaged the XM25. The XM25 has otherwise been very reliable. But these jams are occurring about once every 5,900 rounds fired. The grenade does not explode because the arming device worked but the propellant does detonate during these jams. The XM25 is scheduled to enter mass production this year but the army wants this jamming problem fixed first.

Over the last 18 months over two dozen XM25s were sent to Afghanistan for field tests. This has been a success and XM25 is very popular with the troops. Meanwhile, mass production has been ordered, and this will result in over 12,000 of the weapons being delivered, starting in 2014.

It was obvious that the XM25 was a success after only 55 of the 25mm rounds were fired in combat. The users protested having to give them up after the few months of field testing. All this is because the XM25s worked as advertised, firing "smart rounds" that explode over the heads of Taliban hiding behind rocks or walls or hiding in a cave or room. Enemy machine-guns have been quickly knocked out of action and ambushes quickly disrupted with a few 25mm shells. Encounters that might go on for 15 minutes or longer, as U.S. troops exchange fire with hidden Taliban, end in minutes after a few 25mm rounds were fired.

American infantry love gadgets and they are extremely eager to get electronics that help them in combat. The XM25 combines all that into a very effective weapon. All this came after years of testing and debating whether the XM25 was ready for a combat test. In 2010 the army finally sent five of its XM25s to Afghanistan. This was supposed to happen in 2008, but testing kept revealing things that needed to be tweaked. The first troops to get the initial five XM25s were paratroopers.

The years of testing and tweaking, in response to troop feedback, paid off. Even the current batch of users had suggestions for improvements, and some of these were incorporated in each batch built for testing in Afghanistan.  The mass production model will have still more changes. The troops also asked for a longer range (700-1000 meters) round but this would probably require some major engineering and testing. Such longer ranges are required in a place like Afghanistan, where there's a lot of open terrain, surrounded by hills and places for hostile gunmen to fire from. Yet even with the current model, it's obvious that the XM25 gives the troops something they need and now want. The XM25 won't win the war by itself, but it will make life much more precarious for Taliban fighters.

In development since the 1990s, the XM25 went through several major design changes. The first six XM25s were delivered to the U.S. Army for troop testing in 2005. Two years later a few were sent overseas for testing in combat situations. While the troops have been very enthusiastic about the new weapon, there were a lot of suggestions, mostly about minor items. So the army kept tweaking and refining the weapon.

The XM25 was originally one of two weapons (the other being a 5.56mm rifle) incorporated in the 8.2 kg (18 pound) XM29 OICW (Objective Individual Combat Weapon). The OICW was originally developed as a replacement for the 40mm grenade launcher, with the intention of giving the grenadier some rifle firepower as well. That didn't work out as intended.

The big problem was effectiveness. The older 40mm, unguided, grenade rounds weigh 540 grams (19 ounces) each, the original 20mm OICW round weighed half that. This was one of the 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 consistently, especially compared to the 40mm shell it was replacing. So, in August, 2003, it was decided to take the 5.56mm portion out of the OICW and develop it as a separate weapon (the XM8) and develop the grenade launcher part that fired the "smart shell" as the XM25. But the XM25 would now use a 25mm shell, which would generate 50 percent more fragments (and heavier ones at that) than the 20mm shell of the OICW.

The 20mm and 25mm "smart shells" both use a computer controlled fuze. The XM25 operator can choose one of 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 (19 foot) radius from the exploding round. 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 smart shells can be used out to 700 meters but not as accurately. At those longer ranges, you can't put a shell through a window but you can hurt a crowd of gunmen standing outside the building.

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 5.5 kg (12 pounds). The 25mm shells weigh over half a pound each (270 grams). 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 XM25 capable of knocking out light armored vehicles. Then there are the new versions of the 25mm round, like 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. With the XM25, hiding behind rocks, trees, walls, or in caves will no longer protect you. There is also a flechette ("shotgun") round. The magazine holds four rounds, which cost, on average, $35 each. The XM25, with its 4x thermal sight, costs $25,000.

Meanwhile, an Israeli firm has come up with a cheaper and more appealing (to the combat troops) solution. This is the MPRS (Multi-Purpose Rifle System) which is a 750 gram (1.5 pound) device that is attached to the rail on top of assault rifles (like you would a scope). The MPRS has another attachment for the 40mm grenade launcher that many assault rifles have mounted under the barrel. This cable carries data to a special 40mm grenade, programming it to explode at a specific point (inside a room, behind a rock wall, and so on). The MPRS is basically a sophisticated sight, with a laser range finder, a computer, and an automated aiming system. The gunner picks the target, presses a button to have the laser range finder get the range, and then MPRS programs the 40mm shell, which is then fired. The MPRS can put a 40mm grenade through a window at a hundred meters. Unguided 40mm grenades have a range of about 400 meters but accurate fire at longer ranges is possible with MPRS. The 40mm grenade explosion can kill within five meters and wound up to ten meters or more. The “smart” 40mm round costs less than $50 each. MPRS costs less than $10,000, which is a lot cheaper than the other solution, the XM25. The larger 40mm grenade does more damage and troops don’t have to carry the XM25 with them, meaning one soldier out of ten would not have an assault rifle. If you want to take “smart grenade” capability with you, you just have one solider (the one or two per squad whose assault rifle has the 40mm grenade launcher mounted under the barrel of their rifle) carry the 7 kg (16 pound) bag with the MPRS scope and six rounds of 40mm smart shells. This is cheaper and more convenient than the XM25 and delivers a bigger bang (grenade). This puts some pressure on the XM25 manufacturer, because if they cannot deliver reliable XM25s, the army has an attractive alternative in the MPRS.




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