Give it up for Sandra Bullock and Melissa McCarthy. You’ll never see them work harder at comedy than in “The Heat,” a stumbling, aggressively loud and profane cop buddy picture where they struggle to wring “funny” out of a script that isn’t.

Plot? It’s more a collection of scenes that force the stars to riff and riff until something coarse and amusing comes out, topped by something else coarser and more amusing. Instructions must have read, “Sandy and Melissa go to a dance club, where Melissa hacks off chunks of Sandy’s costume to make her ‘sexy.’” Or “Melissa and Sandy get drunk in a bar and line dance.”

Better still, “Our intrepid, mismatched ‘buddies’ are tied up by the bad guys and turn a simple leg stabbing into a comic escape attempt.”

Bullock, finally back to making the sorts of “Miss Congeniality” dogs she was doing before “The Blind Side,” is the know-it-all overly-coiffed F.B.I. agent Ashburn ― a Miss Priss none of her fellow agents like. She is sent to Boston, ostensibly to prep for a promotion. Mainly, it’s to get her out of the hair of her boss (Demian Bichir).

That’s where Ashburn runs afoul of the foul-mouthed detective Mullins (McCarthy), a shambling train wreck of the American junk food diet run amok. She’s so irritable that her boss (Tom Wilson of “Back to the Future”) is as afraid of her as her favorite drug-dealing perp (Spoken Reasons is this caricature’s stage name).

Ashburn, who has been a bit of a Bullock in a china shop up to now, has met her menacing, mouthy match.

The jokes ― often a string of profane threats strung together by McCarthy ― have a sitcom / stand-up rhythm: ba DUM bum.

Director Paul Feig, whose life changed with the fluky blockbuster “Bridesmaids,” shoots Bullock in her requisite vanity lighting and McCarthy at her chef-pants wearing worst. For a guy who has spent much of the year defending McCarthy from “Identity Thief”-based insults about her short height and considerable width, he’s certainly not shy about using those attributes for a laugh.

And McCarthy, like Bullock, is nothing if not game. She wriggles through car windows, takes pratfalls, wrestles with Bullock to be the first through doorways and swaggers through the picture in the same costume, first scene to last. The woman is funny, and many of her scenes deliver a wincing comic punch.

The fact that we meet her braying Boston family (Jane Curtin is her shrill mom) and that McCarthy’s the only one who didn’t attempt the accent? We don’t dare call that lazy.

Which is more than you can say about Katie Dippold, the screenwriter.

But it’ll be a hit, Feig will work again, Dippold will get another shot and McCarthy will roll on. She has the timing, the riff repertoire and that ineffable something that film fans have loved in comics from Fatty Arbuckle and Oliver Hardy to Belushi and Chris Farley.

We’re just not allowed to say what that is.

By Roger Moore 

(McClatchy-Tribune News Service)

(MCT Information Services)