yaw: The heading of a bullet, used in external ballistics that refers to how the Magnus effect causes bullets to move out of a straight line based on their spin.
x-ring: a circle in the middle of a shooting target bullseye used to determine winners in event of a tie.
windage: The side-to-side adjustment of a sight, used to change the horizontal component of the aiming point.
wildcat cartridge or wildcat: A custom cartridge for which ammunition and firearms that are not mass-produced. These cartridges are often created to optimize a certain performance characteristic (such as the power, size or efficiency) of an existing commercial cartridge.
wheellock: an obsolete mechanism for firing a firearm.
WCF: An acronym for a family of cartridges designed by Winchester Repeating Arms Company, called Winchester Center Fire, as in the .30-30 WCF or .32 WCF
wadcutter: A special-purpose bullet specially designed for shooting paper targets, usually at close range and at subsonic velocities typically under 800 ft/s (240 m/s). They are often used in handgun and airgun competitions. A wadcutter has a flat or nearly flat front that cuts a very clean hole through the paper target, making it easier to score and ideally reducing errors in scoring the target to the favor of the shooter.
trigger: A mechanism that actuates the firing sequence of a firearm. Triggers almost universally consist of levers or buttons actuated by the index finger.
terminal ballistics: A sub-field of ballistics, is the study of the behavior of a projectile when it hits its target.
stripper clip: A speedloader that holds several cartridges together in a single unit for easier loading of a firearm's magazine. A stripper clip is used only for loading the magazine and is not necessary for the firearm to function.
squib load, also known as squib round, pop and no kick, or just squib: A firearms malfunction in which a fired projectile does not have enough force behind it to exit the barrel, and thus becomes stuck. Squib loads make the firearm unsafe to shoot, unless the projectile can be removed.
speedloader: A device used for loading a firearm or firearm magazine with loose ammunition very quickly. Generally, speedloaders are used for loading all chambers of a revolver simultaneously, although speedloaders of different designs are also used for the loading of fixed tubular magazines of shotguns and rifles, or the loading of box or drum magazines. Revolver speedloaders are used for revolvers having either swing-out cylinders or top-break cylinders.
snubnosed revolver: a revolver with a short barrel length.