They are called riflings
The bore refers to the hole in the gun barrel thru which the projectile (bullet) passes. Some guns have a smooth bore, but many modern guns, both pistols and especially rifles, have a rifled bore, that is, the bore has a helical (spiral) groove that causes the projectile to spin as it flies thru the air. The diameter of the gun's bore determines the size of the bullet or shell (e.g. .22, .45, 9mm, etc.)
breech
The bore of a gun relates to the diameter of the hole in the barrel - and in turn the diameter of the bullet the gun can fire.
get a bore attachment to a screw gun or drill.
Caliber "Caliber" is a word for the diameter of the bullet or the bore of the gun.
For guns, a "smoothbore" is a gun that was smooth on the inside of the barrel(or bore). These were also called "muskets" or "smoothbore musket". Later, gunsmiths began to cut a spiral groove in the bore which was called "rifling" that gave a spin to the bullet, resulting in a straighter trajectory and longer range. These were called "rifles".
What are you asking?
bore diameter
The bore is the inside of the barrel- that is, the hole that the bullet is fired through. The diameter of the bore is measuring how wide the bore is from one side to another.
The range is not directly related to bore diameter. And the largest gun over built (The Tsar bombard) has a 36" bore.
It depends on the caliber of the bullet.
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