What is the purpose of lands and grooves on a gun?

Answer 1

When muskets were rifled, the gunsmith used a bit to carve grooves in the length of the barrel. The groove is a depression cut, which created a lan, which was the uncut area. Rifling served to impart a spin on the projectile, which stabilized the flight of the bullet, helping it to travel farther and more accurately. The Minie ball, which is a conical shaped bullet, was hollow at the base, with a skirt about 1/16" of an inch thick and about 3/16 in depth. When the black powder ignited behind the bullet, the force of the explosion caused the skirt to expand, engaging the soft lead bullet into the rifling, thus causing the bullet to spin.