Very important. It's what stablises the projectiles, which gives them their accuracy and range.
In the mid 1400s
Smooth bores are bores or barrels in guns that do not contain rifling. Rifling is made up of lands and grooves that cause the bullet to turn within the barrel of the gun. This turning gives the bullet and gun its accuracy. A smooth bore gun is much less accurate than a rifled bore gun.
Rifling in the barrels
Depends on the maker. Some gun barrels are the finest quality type 4140 chrome moly or 416 stainless steel with button rifling. Hi-Point pistol frames are made from a high-impact polymer and barrels are from an alloy stainless steel.
ALL rifles have barrels that contain "rifling". This is usually in the form of spiral grooves cut into the inside of the barrel- a few have a non-round barrel, with flat surfaces that twist as you go up the barrel. At one time, ALL shotguns had smooth bores- no rifling. However, SOME shotguns now have barrels with rifling, used to shoot slugs. They are still not rifles, as they are meant to shoot shotgun shells.
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.
A gunsmith would've made the barrel, and the rest of the parts required for the gun as well. For the most part a blacksmith made tools and farm equipment. A gunsmith typically would use a lathe to bore out the barrel once it had been made, which was a process in itself, dropforging onto a mandrel before small adjustments and some milling were done. Once the bore was complete many early gun barrels would be ready for the assembly of the gun. In most cases with a smooth-bore the lack of rifling negated the need for the lathe at all. In later years, (civil war era) a rifling breach was used to apply rifling to the inside of the barrel. This greatly improved accuracy and muzzle velocity.
The barrel is bored, and rifled with a cutter or broach. Match barrels are frequently lapped (polished) with a lead lapper coated with very fine abrasive. This lapping polishes out tool marks left by the rifling process, and insures uniform diameter of the bore.
Essentially the same
Type of rifling/twist.