Chamber or barrel.
breech
Chamber
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.
What are you asking?
Something I would run away from. Gun powder BURNS, it does not explode.
bore diameter
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.)
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.