A Definition of the Term 'Round' in Firearm Shooting

Smoking Bullets Falling on Ground
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In the world of firearm usage—including hunting, shooting competition, and professional applications such as the military or law enforcement—the term round refers to a single unit of ammunition before it has been fired. Although sometimes used to refer to the bullet projectile, this is an incorrect usage. 

For a gun that uses cartridge-style ammunition, the term round refers to the outer metal jacket along with its projectile (the bullet) and its internal powder load (propellant), and primer cap. For shotguns, the round refers to the plastic or paper shell casing as well as the pellets or slug it contains; and for muzzleloader guns, the round is the powder load along with the projectile. These components comprise a round only up to the point where the gun is fired. 

The term round is usually reserved for a single unit of ammunition for handheld firearms. Although it is sometimes used to refer to the large ammunition used in military artillery, for those larger guns the term shell is more commonly used. 

The term round should not be confused with the ​bullet, which refers only to the metal projectile that accelerates down the gun's barrel when the trigger is pulled. The bullet itself ceases to a component of the round as soon as it begins moving down the barrel of the gun. 

Origins of the Term

There are several theories as to the origin of the term round, none of them regarded as definitive:

  • The genesis of the term round may be because almost all ammunition cartridges and shotgun shell casings are cylindrical in shape, and thus can be called round.
  • In the early shooting of musket guns in military exercises, firing a weapon involved a several-step process of loading the gun, stepping up to a firing line, and discharging the weapon upon receiving an order. The entire process of loading-preparing-firing was known as a round.  Over time, the mean of the term narrowed to refer to a single unit of ammunition.  
  • Historically, a round was sometimes used to refer to a discharge by a group of military weapons all at the same time. By modern times, the term became gradually become associated with a single unit of ammunition. 

Alternate Meaning

In the sport of skeet shooting, the term round may also refer to a 25-shot session of shooting.