Hello, can anyone tell the correct size of the chokes for a 16 ga shotgun. someone said .662 is the bore size, another said .670. A gunsmith measured my Chokes at .660 IC for the right and .651 mod. for the left. Another gunsmith said .652 is IC & .642 is Mod. . What are the true diamentions.

Hello, can anyone tell the correct size of the chokes for a 16 ga shotgun. someone said .662 is the bore size, another said .670. A gunsmith measured my Chokes at .660 IC for the right and .651 mod. for the left. Another gunsmith said .652 is IC & .642 is Mod. . What are the true diamentions.

This is what I have in my resources... I have included the bores for 16 ga only...

The following is a generally agreed upon list of shotgun TRUE BORE DIAMETERS all gauges (NON-BACKBORED BARRELS) and a Iist of generally accepted choke constrictions (IN THOUSANDS OF AN INCH) for the various named choke constrictions.
(EXAMPLE: You have a 12 gauge shotgun with a true bore diameter of .729 and have .019 choke constriction--therefore you have a MODIFIED choke with an inside diameter of the the choke to be .710.)
MISCELLANEOUS
1. Non-American shotguns (12 GA.) normaIly have a true bore diameter of approximately .005 less than US barrels or generally have a true bore diameter of .725.
2. Back bored barrels (12 GA.) usually have a true bore diameter of .740 to .745.


True Bore & Cylinder Bore Dia. 16ga = .667

Skeet I = .004 - .663

Improved Cyl. = .007 - .660

Skeet II = .010 - .657

Modified = .015 - .652

Improved Mod. = .020 - .647

Full Choke = .028 - .639

Extra Full = .035 - .632