bust a cap 

To fire a gun (military slang from the days of percussion cap and ball firearms before the manufacture of individual cartidges consisting of a metal casing holding a bullet, gunpowder and a primer that fired when struck by a firing pin or hammer.)

We heard some people busting caps a couple of klicks up the trail.

bust a cap by jeff August 13, 2004

bust a cap 

This is not a new phrase as much of the Rap culture would like us to believe. Instead it is an old phrase to shoot someone. Reference to cap is a word for powder cap used in percussion guns popular in the old west. This phrase is used in the 1969 movie titled "True Grit" with John Wayne, Glen Campbell, Dennis Hopper and Robert Duvall.

Line by Ned Pepper (played by Robert Duvall) "I never busted a cap (bust a cap) on a woman or nobody under sixteen. But I'll do it."

bust a cap by J Keto March 10, 2008

bust a cap 

I found this reference to "bust a cap" in a 1951 Gene Autry novel. Gene Autry and the Golden Ladder Gang by W. H. Hutchinson. Whitman 2349

"I guess it is," said Pres as he regretfully fondled the stock of his rifle, "but I surelee hope that somebody gives me a little excuse to bust a cap in their direction."
-- Gene Autry and the Golden Ladder Gang 1951

bust a cap by Nick Boxtop May 11, 2018

bust a cap 

Attested in "True Grit" by Charles Portis, 1968, but most likely much older.

The derivation is probably from the percussion "cap," a small metal cylinder open at one end with an amount of shock-sensitive explosive, usually fulminate of mercury, used to set off the powder charge in a muzzle-loading firearm.

The modern derivation, however, is probably from the "cap gun," a toy firearm using paper "caps" containing Armstrong's mixture or a similar substance to provide the small explosions.

"I have never busted a cap (bust a cap) on a woman or anybody much under sixteen years but I will do what I have to do." -- "Lucky" Ned Pepper

bust a cap by ET Molligee September 20, 2014

Bust a cap 

A slang phrase referring to the posession and use to a certain individial of a firearm or any other object resembling a firearm that emits any sort of a projectile.

"Imma bust a cap in yo mothafuckin ass bitch!"

Bust a cap by www.blingblingx.da.ru November 30, 2004

bust a cap 

To discharge a handgun, usually a 9mm, in the direction of an enemy or a rival gang.

Im gonna bust a cap in his punk ass

bust a cap by HeavenlyHost July 4, 2003

Bust a cap 

To discharge a round of ammunition from a firearm, usually a handgun.

Fuck wit me, and I'll bust a cap in yo ass biatch!!!!
That fool was disrespectin' a brutha so I had to straight bust a cap in his ass!

Bust a cap by Streetsouljah September 16, 2008