The UK Ministry of Defence has turned to famed techsploration firm BBN - which among other things gave the world the "@" symbol in email - to provide a shoulder-mounted gunshot detector able to backtrack bullets in flight and locate enemy gunmen firing at British troops.

Most users will probably not remain this calm in field use.

We learn this courtesy of US-centred arms mammoth Raytheon, which bought up BBN a year ago. Raytheon say that the UK's defence research labs have tested several different shot-spotter systems and found BBN's "Boomerang Warrior-X" to be the best. Apparently the tests are "related to urgent operational requirements".

The Boomerang Warrior-X features a shoulder-mounted module weighing less than 11 ounces (312g) which will run for a day on 2 AA batteries. It works like most such systems by detecting the sonic boom of a passing bullet (bullets do not whistle by, but crack or snap*) and the muzzle blast of the gun that fired it. Together the two sound signatures, provided that the system has got the right pair, can be used to calculate a range and bearing to the gun muzzle in less than a second. This is often a lot faster than troops under fire can locate the enemy who is shooting at them.

There are various other acoustic shot-detectors out there and US forces have thousands in the field already. Thus far they have won mixed reviews: the tech usually works fine given a single unambiguous gunshot to work with, but tends to have problems if several guns are firing - especially if muzzle blasts are also echoing from nearby buildings or terrain features.

BBN's Warrior-X is quite recent, however, and the company claims a low false-alerts proportion of 2 per cent. The selection of the system by the MoD's Defence Science and Technology Laboratories is certainly something of an endorsement - but it doesn't necessarily mean that the problems of acoustic shot-spotters have been fixed well enough to make them useful.

The next stage in the UK's progress will see the Warrior-X trialled "in theatre conditions".

"Sending Boomerang Warrior-X to the field will provide UK troops with the very best protection available," says Boomerang exec Mark Sherman, hopefully. ®

*With the exception of subsonic rounds. These are rare in serious gunfights, however.