Amount of muzzle constriction
The Nobel Hayen Model 602J 20 gauge shotgun typically features a fixed choke, often with a cylinder or modified constriction. The specific choke can vary depending on the production year and configuration of the shotgun. To confirm the exact choke type, it's best to refer to the manufacturer's documentation or check the markings on the shotgun itself.
A barrel with a full choke.
System of changable shotgun choke tubes made by Mossberg. Accu Choke is their brand name. A shotgun choke is a means of reducing the bore size at the muzzle of a shotgun, to produce shot patterns that spread to a greater or lesser degree.
Cylinder bore- no choke at all.
A pattern of a shotgun is determined by the choke at the factory. Some models have a variable choke that makes the user able to change the pattern.
They came in various barrel lengths and choke combinations. If it is not marked on the side of the barrel, you will have to pattern the shotgun to determine the choke
A shotgun barrel with a cylinder bore choke.
Yes- that is what the poly-choke is for.
No
To focus the pattern of shot.
A poly choke is an aftermarket choke. The choke twists to different settings. It should have marks to determine settings around the collar of the choke
Depends on the load and what the maker of the choke/shotgun say.