A barrel is part of a gun
The gun barrel is the metal part that the bullet comes out of.
the barrel is the part that the bullet travels through once the gun is fired. it is on the inside of the gun.
The diameter
It is called a tubular magazine. the action
Get a shorter barrel and swich it out or saw off part of the one you have.
Grooves
Yes, it is called "spiking", although it is likely to cause the barrel to explode if the gun (or artillery piece) is fired. YOU CANNOT PREVENT A GUN GOING OFF, BY INSERTING YOUR FINGER INTO THE BARREL
Looking for someone with history of a single barrel shot gun with wells Fargo & co on barrel and four notches also on gun like to know if its from the stage coach era as the shot gun is called coach
The one in the front is called the "Front Sight". The one in the back is called the "Rear Sight".
Threaded
It's called the Muzzle