Gerard Butler has never been more detestable on screen than he is in “Den of Thieves.” He goes full “Training Day” — OK, half “Training Day” — for a heist thriller about ruthless cops hounding after murderous bank robbers.

It’s not just an homage to Denzel’s dirty cop classic, but an overreach for Michael Mann’s cops/bank robbers classic “Heat.” Hey, if you’re going to knock off genre pictures, go for the best.

“Den” is an overlong, slow-footed, bloody-minded and eye-rollingly “intricate” thriller that follows two rival “gangs,” a “crew” led by Merriman (Pablo Schreiber, half-brother of Liev, star of “Orange is the New Black” and “13 Hours”), and “The Regulators,” a half-dozen LA Sheriff’s Dept. “Major Crimes Unit” specialists who bend the rules and break the law to solve crimes in “the bank robbery capital of the world,” Los Angeles.

The Regulators are led by Big Nick, an “original gangsta cop” played by Butler. He’s a glib brute, the sort of guy who wanders into a crime scene, cracks “That looks like it hurt” to a corpse, eats donuts dropped by a shooting victim (Evidence?) and bullies the wife he cheats on, suspects and the FBI agent he swaps insults with.

“You pausing for dramatic effect?”

Nick and his team finger the recently-released ex-con Merriman as their guy, and immediately taser and kidnap a known associate (O’Shea Jackson of “Straight Outta Compton”).

The threats Nick makes to him are explicit.

“Do we look like the type who’ll arrest you? We just shoot you…less paperwork!”

Donnie (Jackson) is “just the driver,” he insists. But in a flash, he’s caught between two ruthless gangs that could kill him and get away with it. He’ll provide tips about what his robbing crew are up to, and the cops will let him keep his freedom.

“London Has Fallen” screenwriter turned writer-director Christian Gudegast opens with a bloody armored car robbery where guards and one gangster are gunned down and tops that with a few nicely constructed parallel structure sequences. The crooks case their “big” job as the cops try to second-guess their next move and reason-out their behavior.

A clever twist — the crew is ex-military, comfortable with weapons, savvy to the jargon of “tac up” (put on your tactical gear), “deploy” to set up “suppressing fire.” That too-neatly matches up with a police force that’s been similarly militarized.

Another twist, left undeveloped? Merriman’s connection to LA’s Samoan (big, burly Islanders) underworld.

It’s the kind of picture that doesn’t have an easy time finding somebody for the audience to root for. There are plot twists that are too far-fetched for the script to organically justify, and heist picture cliches (air ducts, open sewers, hostages, red herrings). Scenes that don’t advance the plot but do develop character abound — Nick bullying his soon-to-be-ex’s new beau, one of the crew (50 Cent) playing an alarming joke on his daughter’s prom date. Pacing is a serious problem with what should be a “ticking clock thriller.”

Butler and Schreiber have a couple of scenes together, not quite in the DeNiro/Pacino “Heat” league, but novel and played with movie moxie. The cop stalks his quarry to his favorite firing range, where the two gun nuts compete to show off who’s the best shot. If you thought “Proud Mary” fetishized firearms, you ain’t seen nothin’ yet.

The women here are mostly strippers, hookers and the wife (Dawn Oliveri) Nick is probably cheating on. If #Timesup wants to look for productions where women are mistreated, exploited and worse, start with thrillers peopled with nameless prostitute characters and the obligatory strip club scene.

And you have to wonder if pictures like this, depicting armed and body-armored crack-shot criminals with all manner of weapons, intelligence and limitless technological support, aren’t a part of why America’s police are increasingly militarized and alarmingly trigger happy. “Den of Thieves” is a war movie — complete with epic combat-style shootouts, endless titles pinpointing the scores of locations — “San Pedro, Wilmington, Torrance, Monterrey Park” — but with cash as the ultimate objective.

I can’t say it wasn’t interesting to sit through, slow-moving as it is, but “Thieves” never rises above a seriously long-winded B-movie, a shoot-em-up in which no matter how graphic the violence that the characters mete out and witness, nobody ever lets you forget they’re playing cops and robbers.

The bravado gives away that one and all know nobody gets hurt here. The blood and bullet holes created by a blizzard of spent shell casings aren’t real. You’d swagger and wise-crack too, if you knew at the end of the day all you had to worry about was where to spend the movie’s money after you’ve wiped the fake-blood off.

MPAA Rating: R for violence, language and some sexuality/nudity

Cast: Gerard Butler, Pablo Schreiber, O’Shea Jackson, Curtis “50 Cent” Jackson, Evan Jones

Credits: Written and directed by Christian Gudegast . An STX release.

Running time: 2:20