An R-rated horror action comedy fairy tale — how’s that for genre bending?

“Hansel & Gretel: Witch Hunters” is more Gatling guns and grenades than The Brothers Grimm. It takes the kidnapped kiddies into adulthood, where they’ve parlayed their fame at cooking a witch’s goose into a business. Got a witch problem? Call H & G — the extermination experts.

High concept pitch or no, the movie doesn’t really work. They were shooting for sort of a witch-hunting “Zombieland,” an f-bomb-riddled “Van Helsing” packed with comical anachronisms — a Bavarian forest past with witch trials, pump shotguns and primitive tasers, where bottles of milk have woodcut pictures of “missing children” on the labels.

Hansel (Jeremy Renner) and Gretel (Gemma Arterton) show up just as the village of Augsburg is about to burn a redhead. “Gingers” were a favorite target of witch hunters. Hansel shrugs this barbaric crime off, but Gretel insists that the locals need “evidence.”

That puts them in conflict with the sheriff (Peter Stormare), who can’t get a handle on their “witch plague” and the missing children who come with it. H & G have been hired to do what he cannot.

It isn’t long after Hansel mutters “Anyplace we can get a drink in this hell hole?” that the siblings are on the job, chasing lesser witches in pursuit of the Great Witch, played by Famke Janssen as if the makeup is going to do all the acting for her.

And there may be troll involved.

“Trolls are extra,” Hansel growls, always watching their bottom line.

Hansel and Gretel have a groupie (Thomas Mann), and the woman Pihla Viitala) they saved from burning in the opening scene wants to repay the favor to Hansel, a repayment that involves skinny dipping. And when they’re on the clock, they have all manner of clever gear to help them battle the wand-wielders — pistols, rifles, a semi-automatic crossbow, the aforementioned taser (hand-cranked).

Writer-director Tommy Wirkola focuses on the fights and flings all manner of viscera at the 3-D camera as limbs are whacked off and heads and torsos explode. Less attention was paid to the story, and the dialogue is a tad over-reliant on the random f-word to land a laugh.