Grooves cut into the inside of a gun barrel for the purpose of spinning the bullet when fired.
It causes the bullet to spin which makes it go straighter.
Rifling a gun barrel causes the bullet to spin when it comes out. This makes the bullet fly more straight and greatly improves accuracy. Much like a spinning football spirals.
Inside the barrel.
Lands and grooves.
You compare the rifling marks on the bullet to the rifling in the barrel. You can also compare the firing pin mark on the primer to the firing pin on the gun.
Essentially the same
Type of rifling/twist.
Rifling will leave grooves--impression in a bullet. These grooves can indicate the manufacturer of the gun that fired that bullet, AND, if there is a suspected gun in particular, microscopic variations can be used to confirm or refute that gun's involvement to a high degree of certainty.
The rifling in a firearm is designed to cause the project (bullet) to spin, increase stability and accuracy.
shot gun and very early muskets
The twist on the inside of a gun-barrel is called rifling. I dont know the specific pitch of the rifling in this particular gun but thought you would like to know the proper terminology.