Just about everybody in “Free Fire” sustains multiple gunshot wounds, to the legs, the arms, the shoulder, the buttocks, you name it.

When they’re shot, they scream in pain and they vow revenge — but time after time, they shake it off and they continue to limp about, firing their weapons at will until they’re hit again.

Maybe this was how paintball was invented. Maybe one of the survivors of this carnage came up with the idea just before lapsing into a coma.

Director and co-writer Ben Wheatley’s “Free Fire” is set in the 1970s (a few years before paintball was invented) and is set almost entirely in a Boston warehouse where a cash-for-guns deal goes horribly wrong, igniting a movie-length shootout featuring about a dozen total Bad Guys and Even Worse Guys (and one Badass Woman).

And hey, there’s little danger of anyone running out of weaponry or ammo, because they’re all in that warehouse for a gun exchange. How convenient!

This is a less clever “Reservoir Dogs,” with many an homage to the Tarantino classic, from the remote warehouse setting to the use of 1970s pop music (hello, “Annie’s Song” by John Denver) to characters who get shot dead in their tracks in mid-dialogue to the ending itself.

But whereas “Dogs” occasionally left the blood-spattered warehouse for flashbacks that provided a back story and fleshed out some of the characters, “Free Fire” puts everybody in the room within about five minutes — and that’s where we stay for the rest of the journey.

Either you’re in the mood for a series of gruesomely creative kills and lots of dark humor — or you’re not.

Either you’ll get a kick out of Academy Award winner Brie Larson becoming bloody and muddy and nasty as she shoots to kill and takes a few hits of her own — or you won’t.

Either you’ll crack up when a guy who’s on fire grabs a nearby extinguisher and tries to use it on himself like a shower head — or …

Well. You get the idea.

The cavernous, shuttered factory warehouse in “Free Fire” is set on the outskirts of Boston. “Whatever they made here, nobody wants it any more,” observes one character. (The reveal of what was manufactured at the warehouse makes for an extended visual gag worthy of an old silent movie.)

Cillian Murphy is Chris and Sam Riley is Stevo. They’re here to buy guns for the IRA.

Sharlto Copley is Vernon, Babou Ceesay is Martin and Jack Reynor is Harry. They’ve got the guns.

Armie Hammer is Ord and Brie Larson is Justine. They’re the dealmakers who put this thing together, from different angles (Ord working with the gunrunners, Justine cozying up to the IRA bunch).

That’s not everyone in the warehouse, but it’s a start. Suffice to say you can trust nobody, everyone’s a hard case and the moral compasses of the whole lot have long ago been shattered.

Wheatley directs “Free Fire” as a cliché-riddled B-movie that loves cliché-riddled B-movies. Chuckling, smug characters get their comeuppance. Characters point guns at vulnerable enemies and pull the trigger — only to learn, yep, they’re out of ammo. The tables are turned, and turned again, to the point where loyalties are thrown out the window.

There’s even a speck of romance between Cillian’s Chris and Larson’s Justine, who somehow find time for a little awkward romantic banter between dishing out and/or sustaining serious bloodshed.

The semi-outrageous fashions and the aggressive facial hair mirror the times quite well. The dark warehouse, filled with potential props once the shooting begins, proves to be a video-game-worthy setting. And the ways in which Wheatley moves the excellent cast around the warehouse are impressively creative.

Armie Hammer has a gift for deadpan humor, and it’s put to great use here. Cillian Murphy is the closest thing to a hero (or at least anti-hero we can root for) in the movie. Brie Larson is a gamer. Her Justine has a sweet face and seems most interested in everyone getting out of the encounter alive — but there’s more to Justine than meets the eye.

“Free Fire” kills.

 

★★★

A24 presents a film directed by Ben Wheatley and written by Wheatley and Amy Jump. Rated R (for strong violence, pervasive language, sexual references and drug use). Running time: 90 minutes. Opens Friday at local theaters.