A shotgun barrel that has no choke or narrowing towards the end of the barrel is called a _______ _______ (2 words).

The term "Cylinder Bore" refers to a shotgun barrel that has a uniform diameter from the chamber all the way to the muzzle without any constriction or narrowing. This design allows for the shot to spread more quickly upon leaving the barrel, which can be beneficial for certain shooting scenarios, such as close-range targets or when a wider pattern is desired. Cylinder Bore barrels are versatile and often used for shooting at various distances without the concerns of shot constriction that arises with choked barrels.

In contrast, barrels designated as Full Choke, Modified Choke, or Skeet Bore have specific constrictions that serve to pattern the shot in different ways for various types of shooting such as trap, skeet, or hunting. Each of these options is designed to control how tightly the shot is clustered, but they do not apply to the description of a barrel that is straight and uniform throughout, which is the defining characteristic of a Cylinder Bore.