Fireform - Using the pressure of normal firing to shape a cartridge case to fit a given chamber.


Firing Pin - That part of a gun's mechanism that strikes the primer to start ignition.


Flake Powder - A smokeless powder characterized by thin, disc-shaped granules.


Flash Hole - The hole leading from the primer pocket into the body of the cartridge case. Also called the vent.


FMJ - Full metal jacket. See metal case.


Foot-pound - A unit of kinetic energy in the English system defined as the effort required to raise one pound to a height of one foot against the force of gravity.


Forcing Cone - The slope of the forward end of the chamber of a rifle or shotgun which decreases the chamber diameter to bore diameter. In a revolver, the bevel in the rear of the barrel just ahead of the cylinder.


Form Factor - A multiplier which relates the shape of a bullet to the shape of the standard or reference projectile used to determine the ballistic coefficient.


FPS - Feet per second, a measure of velocity in the English system. Also feet/sec, ft/sec, or fs.


Freebore - The distance, if any, which a bullet travels upon firing before it contacts the origin of the rifling.


Frontal Ignition - Experimental type of cartridge ignition system where primer flash is directed to the forward part of the powder charge through a metal tube.