Be advised that “Dragged Across Concrete” lives up to its title, although it takes most of its leisurely 159 minutes to get to the grisly scene in question. This is a bare-knuckle cop picture that doesn’t hold anything back.

Powered by a strong cast — Mel Gibson and Vince Vaughn lead the way — this movie is another gut-punch from one of the most interesting filmmakers to have emerged in the past few years, S. Craig Zahler. He writes, directs and co-composes the very specific songs in his movies.

“Dragged” opens with a nasty little sequence in which two cops strong-arm their way through a stakeout. Say hello to grizzled veteran Ridgeman (a believably worn-out Gibson, his “Lethal Weapon” energy long gone), and his younger partner, Tony (Vaughn).

Somebody catches their brutal tactics on video, and their superior (Don Johnson) slaps them with a six-week suspension. They can’t afford that, so Ridgeman concocts a foolish plan to hustle some hustlers. Tony, equally foolish, goes along with it.

The plot involves stolen gold, but there’s a lot more happening. We meet an ex-con named Henry (Tory Kittles) who, along with an old friend (Michael Jai White), comes into the robbery from his own angle. And for a while we track a bank teller, Kelly (Jennifer Carpenter), whose connection to the story is initially unclear.

The second half is a sustained look at how a robbery, and the crooked cops’ attempt to horn in on the action, goes very wrong. The story is full of surprises and reversals and gross detail, as well as extensive conversations between the talkative Ridgeman and Tony.

“Dragged Across Concrete” wants to be hard-boiled, and sure enough, it’s a 10-minute egg. At times the film goes out of its way to prove its toughness; Zahler rarely forgets to remind you — the dialogue is full of racist and sexist chatter — of how provocative it’s all meant to be. Some of this feels more irresponsible than edgy.

His previous films, “Bone Tomahawk” and “Brawl in Cell Block 99,” were lean and mean, and altogether more tightly focused than the new one. In “Dragged,” everybody keeps yapping, as though to stir the pot with hot-button references.

At times I wondered if Zahler was kidding us — the plot is crammed with potential cliches. Henry needs the money to help a younger brother in a wheelchair, Ridgeman needs the money so he can move his sick wife (Laurie Holden) and precious daughter to a better neighborhood, and Tony’s a big lug who can’t work up the nerve to propose to his girlfriend.

This film may be all mixed up inside its thick head, but darned if it isn’t compelling. Zahler knows how to make movies, and you’ll be glued to this one even if you disapprove.

“Dragged Across Concrete” (3 stars)

A bare-knuckle rogue-cop picture that doesn’t hold anything back, with Mel Gibson and Vince Vaughn as suspended officers who try a foolish plan to rob some robbers. Even when the film seems irresponsible in its hot-button pot-stirring (and even at a leisurely 159 minutes), director S. Craig Zahler keeps the action compelling. With Tory Kittles.

Rating: R, for violence, language, nudity

Opening Friday: Varsity, digital on-demand platforms