Balanced somewhere between spoof and satire, “Free Fire” blazes through all the familiar tropes of the ’70s-era crime thriller, developing a spirit of absurdist self-referentiality. A cast well stocked with talented goofballs playing trigger-happy killers drives a baby-simple premise past the point of parody into a realm of pure, demented lunacy.

A dozen criminal types meet in an abandoned Boston warehouse, each one carrying a loaded weapon or two. Irish Republican Army member Chris (Cillian Murphy) is there to buy 30 military assault rifles from brazenly dislikable arms merchant Vernon (Sharlto Copely). Suave, sardonic Ord (Armie Hammer) is there to bodyguard the dealer, while token woman Justine (Brie Larson) brokers the exchange. Various lunkhead accomplices are on hand to supply their ragtag services.

A pair of underlings with personal grievances set off a melee, and shots are fired. Through people’s skin. For an hour. Nonstop.

Under normal circumstances, this would be nightmare fuel. Here, it’s maniacal humor.

The setup feels like off-brand Tarantino, married to the cartoon sadism of “The Itchy & Scratchy Show.” Director Ben Wheatley, who also co-wrote the film and drafted Martin Scorsese as a producer, handles its mounting bloodshed with ironic weirdness. Imagine a graphic, gory, violent caper movie where every character is descended from Monty Python’s Black Knight, madly continuing to claim “Just a flesh wound” after losing multiple limbs. At the same time, these sociopaths smirk at each other’s pain. It’s easy to know why Justine rolls her eyes and sneers, “Men.”

This is a strikingly down-and-dirty film. As soon as the bullets fly, the ensemble goes down and stays there, belly-crawling across the grimy floor like rugrats. One of the film’s impressive virtues is its filthy, dangerous situations that are engineered for maximum comic humiliation. While the group slithers across jagged glass and drug syringes, one moans, “Dust is bringing up my allergies.”

The dirty dozen are all shallow, but each one is sharply drawn. Vern blathers orders in a cowardly tone and a South African accent that confuses everyone. Two guys guess it’s Austrian, because they can’t think of where the kangaroos live. Vern tries to boost his tough man status by declaring, “Africa’s not for sissies,” but a couple of insignificant skin scrapes make him sure he’ll bleed to death. Wheatley would rather torment him with a lot more shots to bones and organs before that happens.

Ord, looking natty in a turtleneck and styling his hair when he finds himself in a mirror, has the wittiest conversation. Preparing to run away from a gunman, Vern commands Ord to “distract him with your badinage!”

Beyond showing people shot in body parts that films have never shown before, Wheatley, a Brit who has directed episodes of TV’s “Doctor Who,” sweats details that operate on a nearly subconscious level. Veteran sound editor Martin Pavey (who also has 13 composing credits) created the film’s elaborate sound design. Not only does each weapon make a different noise, each bullet hit on stone, metal, wood or flesh has a tone all its own. Multiply that for ricochets.

The audio also reproduces the melodies of John Denver eight-track tapes and recorded phone solicitors with uncanny accuracy. The action on-screen is continuous pandemonium, but there’s no chaos on the technical side.

“Free Fire” is a one-joke movie, and it’s a pretty fresh joke. Great art it’s not, but the laughs-per-minute ratio is impressive. Call it flawed and fabulous.