Jacket
The hard metal covering surrounding the lead core of a bullet.
Jacketed bullet see Bullet, jacketed
Jaws
Part of a flintlock cock, the vice like mechanism that holds the flint.
Jezail
A long barrelled crooked stocked Afgan matchlock, often rifled and sometimes converted to flintlock. The weapons overall length sometimes reaches seven feet.
Jingal
A small portable gun resting on two legs and its butt end.
Jove
The cheek hollow in the butt of a rifle stock.
Jump
The amount measured both vertically and horizontally that the bore axis changes while a projectile is moving from the chamber to the muzzle.