Velocity
Of a projectile, the speed, usually expressed in feet per second.
Velocity, instrumental
Measured at a specific point on the projectile’s trajectory. Such measurements must always include the range at which the reading was made.
Velocity, muzzle
Computed at the initial point of the trajectory, normally the muzzle of the firearm.
Vent
Any small hole, channel or tube designed to conduct the flash of the ignited priming powder from the breech to the propellant charge in the chamber.
Very pistol
A weapon designed to discharge flares for signalling purposes.