A RIFLE capable of firing explosive bullets that can detonate within a metre of a target could let soldiers fire on snipers hiding in trenches, behind walls or inside buildings.
The US army has developed the XM25 rifle to give its troops an alternative to calling in artillery fire or air strikes when an enemy has taken cover and can鈥檛 be targeted by direct fire. 鈥淭his is the first leap-ahead technology for troops that we鈥檝e been able to develop and deploy,鈥 says , the army鈥檚 project manager for new weapons for soldiers. 鈥淭his gives them another tool in their kitbag.鈥
The rifle鈥檚 gunsight uses a laser rangefinder to calculate the exact distance to the obstruction. The soldier can then add or subtract up to 3 metres from that distance to enable the bullets to clear the barrier and explode above or beside the target (see diagram).
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As the 25-millimetre round is fired, the gunsight sends a radio signal to a chip inside the bullet, telling it the precise distance to the target. A spiral groove inside the barrel makes the bullet rotate as it travels, and as it also contains a magnetic transducer, this rotation through the Earth鈥檚 magnetic field generates an alternating current. A granted to the bullet鈥檚 maker, Alliant Techsystems, reveals that the chip uses fluctuations in this current to count each revolution and, as it knows the distance covered in one spin, it can calculate how far it has travelled.
The rifle would allow a soldier faced with a sniper firing from a window to take a distance measurement to the window, add a metre, fire through the window, and have the round detonate 1 metre inside the room. The same method could be used to fire behind a wall or over a trench.
As it stands, Tamilio says, soldiers faced with enemies behind cover have the option of using grenade launchers, which have limited range and accuracy, or asking for artillery fire or air strikes. However, both of those options cover a large area and so have a higher risk of killing civilians, especially in urban areas. They are also expensive. 鈥淵ou could shoot a Javelin missile, and it would cost $70,000. These rounds will end up costing $25 apiece. They鈥檙e relatively cheap,鈥 Tamilio says.
鈥淭his airburst shell gives the close-combat capability of a grenade launcher, combined with the ability of indirect fire weapons to hit stuff on the other side of the wall,鈥 says , a defence analyst with Washington DC think tank GlobalSecurity.org.
Pike says it is just one example of 鈥渟mart鈥 munitions now possible because of microchip advances.
Although the rifle will initially use high-explosive rounds, it might later use versions with smaller explosive charges that aim to stun rather than kill.
The US army plans to field-test prototypes of the rifle soon, possibly in Iraq or Afghanistan, and hopes to begin using it by 2012.
