A report from the set of the film where John Travolta and Nicholas Cage steal each other's looks and acting styles

Fire in the hole, folks! this shot requires ear protection!”

An assistant director barks the warning as a property master hustles up to Nicolas Cage and puts a machine gun in his fist. Looking stark as a charcoal drawing in black jeans, black boots, a black leather jacket, and a black-striped shirt that hugs his heavily worked-out torso, Cage cradles the gun warily. It may be loaded with blanks, but it’s still a 9 mm Mini Uzi, one of the more powerful firearms he brandishes at costar John Travolta in the body-switching melee Face/Off.

Yet it’s not the Uzi’s fearsome killing abilities that seem to interest director John Woo, who left Hong Kong for Hollywood five years ago and now stands at the forefront of an expatriate film-biz boom. What strikes Woo about an Uzi is its visual elegance: the coiled power of the kickback, the superbright yellow flare it emits when it’s fired. So on this chilly February morning in downtown L.A., about two thirds of the way through Face/Off‘s fully loaded 105-day, $80 million-plus shoot, Woo has brought out the heavy artillery — the sort that made his name in his late-’80s/ early-’90s Cantonese-language cult hits The Killer and Hard Boiled — to provide a guiding light.

The sequence is a hall-of-mirrors shoot-out, an aptly symbolic set piece for a story about an FBI agent, Sean Archer (played by Travolta in the movie’s first 20 minutes) who infiltrates the operations of terrorist Castor Troy (initially played by Cage) by having Troy’s kisser lasered off and grafted onto his own. Trouble is, now-faceless nutjob Troy gets loose, appropriates Archer’s preserved puss, and sets out to take over Archer’s job, family, and identity. It’s the sort of good-mixed-inextricably-with-evil premise that brings out Woo’s best instincts, not to mention two all-stops-out performances.

”Ten seconds,” comes the call. Onlookers stuff small foam pellets into their ears; those closer to ground zero don clunky yellow headphones like the ones airport runway crews wear; Cage wears tiny, fitted, flesh-colored plugs. The focus puller and camera operators adjust their protective goggles, ready to dodge an imminent shower of flying debris.

”And…action!” yells a hawkeyed supervisor as Woo watches on a monitor tucked in a corner of the set; there are too many safety issues involved for anybody but a weapons expert to monitor the timing. As Cage steps into a rotunda surrounded by eight full-length mirrors, he sees Travolta’s figure scurry through the columns — or, rather, Travolta’s double, since the actor himself won’t be required for several more hours. On cue, Cage raises his gun and squeezes the trigger.

How to convey the sonic-boom fury unleashed in the next 60 seconds by this incongruously petite gun? Try picturing one of those old ’50s films of a nuclear test blast ripping the fronts off houses. The air pressure in the room surges palpably. Eyes water. The crew members closest to the action can see their T-shirts vibrating. The bass frequencies rumble through you like you’re Wile E. Coyote with a belly full of Acme Earthquake Pills.