percussion cap

a small metallic cap or cup containing fulminating powder, formerly exploded by percussion to fire the charge of small arms.

Origin of percussion cap

First recorded in 1815–25

The revolver of the Civil War was, of course, a percussion-cap weapon.

Rebel Raider |H. Beam Piper
He started running over, in his mind, the paratemporal areas in which gunpowder but not the percussion-cap was known.

Time Crime |H. Beam Piper
On so slight an incident—the defect of a percussion-cap—did the battle hinge.

The Dixie Book of Days |Matthew Page Andrews
First of all—above and beyond everything else in a boy's sight—was the voyageur's percussion-cap rifle.

Strange Stories of the Great Valley |Abbie Johnston Grosvenor

Then seizing one arm, he draws it across the opposite shoulder, until the joint cracks like a percussion-cap.

The Lands of the Saracen |Bayard Taylor

percussion cap

a detonator consisting of a paper or thin metal cap containing material that explodes when struck and formerly used in certain firearms