Chokebore
Chokebore , noun
1.
In a shotgun, a bore which is tapered to a slightly smaller diameter at a short distance (usually 2½ to 3 inches) to the rear of the muzzle, in order to prevent the rapid dispersion of the shot.
2.
A shotgun that is made with such a bore.
Chokebore , transitive verb
To provide with a chokebore.