What travels through the barrel of a handgun or rifle?

Bullets travel through the barrel of a handgun or rifle. When the gun is fired, the ignited powder creates a rapid expansion of gases that propel the bullet down the barrel and out of the muzzle. The design of the barrel, including its rifling, plays a crucial role in stabilizing the bullet's flight path, allowing for increased accuracy and distance.

While shell cases are important components of ammunition, they do not travel through the barrel; rather, they remain behind in the chamber after the firing process. Powder, while vital for creating the necessary pressure to propel the bullet, is contained within the shell casing and does not travel through the barrel itself. Wads are typically associated with shotgun ammunition and act to separate the shot from the powder but again do not travel through the barrel in the context of handguns or rifles.