He’s officially waaaaaay past “boyish,” and he no longer has that cop show set in Hawaii.

But here is high mileage Scott Caan, Hawaiian shirt open to show off his still cut abs, playing a first time hit man in a dead town In the middle of nowhere in the American West. Strutting when he walks, head thrown back, he’s almost the spitting image of his old man.

And in his new movie, a violent, somewhat gritty but lighthearted thriller, all he and his character want is “One Day as a Lion.”

Caan scripted himself a fair to middling tale, had the clout to line up J.K. Simmons, Frank Grillo and Virginia Madsen as supporting players and the good sense to talent-scout Oklahoma-based director John Swab, of “Ida Red” and the Frank Grillo star vehicle “Little Dixie.”

And though it takes a while to serve up that “buy in” moment, damned if Caan, Swab & Co. don’t hit it and exit with a feel-good flourish. Swab’s steadily sharpening thriller skills and Caan’s need to establish himself as a laconic, witty B-movie anti-hero occasion a happy movie marriage-of-convenience.

Jackie is a mug and ex-pug who’s trying to talk himself out having to do this “job” when we meet him. He owes Dom (George Carroll) something. And Dom owes Pauly (Grillo). And the dude Jackie is assigned to whack owes Pauly big-time.

But the gristle-and-sinewy “dude” rides up to his morning diner in BFE, Oklahoma in a saddle.

“You can’t kill a guy on a horse!”

City boys, am I right. But there’s no getting out of that, just get out of your 1970 Olds 442, put on a ridiculous mustache and silly hat and take care of business, boy.

As “Walter,” the target, is played by J.K. Simmons at his flintiest, we know this won’t go well. Walter escapes in a shoot-out. Jackie accidentally shoots the diner-owner, kidnaps irate waitress Lola (Marianne Rendón), and before he can come up with a plan-B, damned if some local hasn’t stolen the muscle car.

“I’m either curreently wanted for murder, or uh, yeah I’m GONNA be murdered by the guys who hired me to murder the guy I didn’t murder.”

Tricky. Luckily, world-weary Lola has some ideas.

Swab lets Caan’s script saunter along a bit too leisurely after a brisk opeing. But that gives this short, sweet and to the bloody-point action pic a time to introduce complications — the gunman’s jailed son (Dash Melrose, now THERE’s a stage name), Jackie’s ex-wife (Taryn Manning of “Orange is the New Black”) and Lola’s bitter, rich and dying “black widow” mother, given a cynical flourish by the great Virginia Madsen.

Grillo dons his wife-beater T-shirt and looks tough and almost amusingly perplexed and Simmons is immovably ornery in their two chewy scenes together.

“This isn’t me scared, boy. This is me pissed off.”

The shootouts are realistically innacurate and ill-conceived — by the shooters. Caan’s a credible brawler and Rendón, of TV’s “Imposters,” gives Lola’s bored to sarcastic to embittered journey layers of hurt and defiance.

I do love me a solid B-movie, and this one, after it finds its footing, delivers. Still not sold on adding Oklahoma to my bucket list, though. But Swab might be getting me there.

Rating: R for pervasive language, some violence and sexual references

Cast: Scott Caan, J.K. Simmons, Marianne Rendón, Taryn Manning, Frank Grillo and Virginia Madsen

Credits: Directed by John Swab, scripted by Scott Caan. A Lionsgate release.

Running time: 1:27