Understand that there is absolutely nothing wrong with the venerable M16 rifle, its fraternal twin the M4 carbine or their trusty sidekick the M203 grenade launcher. It is the enemy who has changed. Military analysts say that in the future there will be fewer Desert Storms and more low-intensity operations, including missions to capture drug kingpins and to rein in regional warlords. Confronting these enemies will draw Army and Marine infantrymen into unwelcome new battlefields. Tomorrow's wars will be fought in the unmapped streets and alleys of the Third World's sprawling slums.

For several years, arms makers have been competing to design the rifle future soldiers would use. It had to be a weapon capable of winning on urban battlegrounds as well as in more familiar desert, forest and jungle terrain. The Pentagon dubbed its dream rifle the "objective individual combat weapon," or OICW.

The winning entry--submitted by an international team of companies led by Alliant Techsystems of Hopkins, Minn.--looks more like a prop from a Buck Rogers movie than anything you've seen at a rifle range. The modular, two-barrel weapon promises to turn foot soldiers into devastating, precision-firing platforms.

The OICW can be a dual- or single-barrel weapon. The removable top barrel hurls 20mm high-explosive air-bursting fragmentation rounds over the heads of hidden targets more than a half-mile away. The lower barrel shoots NATO-standard 5.56mm ammunition. These "kinetic" rounds provide accurate single-round or suppressive fire bursts at distances up to about 500 yards. A single trigger is linked to both barrels, by way of a laser-guided electronic fire-shot system as sophisticated as what you will find on a modern tank.

"OICW will leave no place for the enemy to hide on tomorrow's battlefield," says Don L. Sticinski, vice president of Alliant. Having won the $8.5 million competition, the company will now build seven OICWs and about 4700 rounds of test-fire ammunition. These will be used in an advanced technology demonstration program managed by the Joint Service Small Arms Program Office, at the Army's R&D center in Picatinny Arsenal, N.J.

Commanding General Joseph W. Arbuckle has invited Popular Mechanics to have a look as the first operational OICW undergoes tests at

Picatinny. Program manager Matthew T. Zimmerman, an OICW enthusiast, introduces us to the infantryman's new best friend: "Preliminary testing programs conducted at Picatinny during the past several years have proven OICW is very effective and has awesome destructive power."

Zimmerman says that the key to the OICW's success in urban warfare is its electronic fire-control system, which enables the rifle to determine when its "smart" 20mm ammunition should detonate. Like conventional explosive rounds, these shells will detonate on impact, says Zimmerman. However, they also can be set to explode after passing through a wall or sheetmetal. This capability could be especially useful in Third World shantytowns, where abandoned or pirated cargo containers are popular building materials.

The most impressive and useful feature of these munitions is their airburst capability. "The fuzing technology is key to our system," says Alliant program manager Michael C. Moore. He explains that a laser rangefinder pinpoints the precise distance at which the fragmenting round needs to detonate, killing the enemy even if he is hiding behind trees or walls, or in trenches.

The Army Infantry Center in Fort Benning, Ga., charged with evaluating new technologies and tactics, agrees. The OICW can take out the types of targets that in the past required an M16 equipped with an M203 grenade launcher. The difference is that the OICW can do the job with pinpoint accuracy. This is a critical advantage when enemies hide among civilians--a prime survival tactic in urban warfare. And the OICW's range of 1000 meters is five times greater than what an M16 equipped with an M203 can achieve.

The OICW will shoot 20mm rounds one at a time and 5.56mm rounds in single shots or two-round bursts. For direct fire, OICW has a video camera and a video-tracker function. A special-purpose computer puts electronic brackets around a moving target and automatically determines its range. It doesn't do all the work, though. "You have to be able to hit the enemy with a laser beam in order to know where it is," says Alliant's Moore. "You can't get range information if you can't laze on the guy or near the guy. That's a given. There's no magic in it." It isn't as easy as it looks. The diameter of the laser beam is intentionally narrow to keep the rangefinding computer from being thrown off by background clutter.