Imagine Luc Besson (“The Professional”) shot through with the farcical lunacy of the Zucker brothers (“Airplane”) and the in-your-face topical editorializing of Michael Moore (“Bowling for Columbine”), and you might have something that resembles “Shoot ’Em Up,” surely one of the weirdest, wildest action movies of this or any year.

Does that mean it’s good? Not necessarily. In fact, one is left to wonder how writer-director Michael Davis — known, barely, for the little-seen hitchhiker horror flick “Monster Man” (2003) — managed to lasso a cast that includes Clive Owen, Paul Giamatti and Monica Bellucci with a script so painfully whacked. “Bullet rips through umbilical cord” must read a bit saner on the page than it looks on-screen.

Davis, to his presumptive credit, wastes little time getting down and dirty. Within nanoseconds of the opening credits, grizzled inner-city recluse Mr. Smith (Owen, reviving his “Sin City” persona) has stopped a thug from executing a pregnant woman — by shoving a carrot through the culprit’s neck. I say again, a carrot. For audiences unacquainted with the killing potential of America’s favorite nutritious root, “Shoot ’Em Up” will be enlightening, to say the least.

Mr. Smith’s reluctant act of chivalry has unintended consequences, as he finds himself playing midwife while trading gunfire with an army of leather-clad ruffians and their limerick-cracking leader, Mr. Hertz (Giamatti, slumming it with gusto.) Lethal multitasking is a specialty of Mr. Smith’s — later, he eliminates a squad of commandos whilst having sexual intercourse.

Unfortunately the mother doesn’t survive the ordeal, but the newborn infant does, obliging Mr. Smith to play nanny while enlisting the services of a wet-nurse prostitute named DQ (Bellucci, exquisite, even in this movie). Naturally, this absurd partnership yields all kinds of Bessonesque, creepily sentimental moments, like the scene in which DQ services a client behind a garbage Dumpster so she can buy the baby a Kevlar swaddling cloth.

Set to the songs of Nirvana, Wolfmother and other heavy-metal standards, “Shoot ’Em Up” is a self-conscious monument to excess. The one-liners are intentionally bad, the action scenes purposefully preposterous (at one point, Smith orchestrates a head-on collision with a van of villains so he can fly though the windshield and machine gun them all to death). Finally, as a coup de grace, writer-director Davis postures “Shoot ’Em Up” as an anti-gun parable, complete with villainous firearm magnates and corrupt, Second Amendment-protecting politicians.

Bullets and umbilical cords notwithstanding, this appalling attempt at irony might be the most wearisome gimmick of all.

‘Shoot ’Em Up’

Stars: Clive Owen, Monica Bellucci, Paul Giamatti

Behind the scenes: Written and directed by Michael Davis

Rating: R for violence, sexual situations, profanity

Running time: 87 minutes

Grade: C-