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THE MOST COMPLETE LINE OF SHOTGUN CHOKE TUBES, TOOLING & ACCESSORIES AVAILABLE TO THE SHOOTING INDUSTRY
SHOTGUN CHOKE SPECIFICATIONS (NON-BACK BORED BARRELS)
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.
Gauge 10 12 16 20 28 410
True Bore Dia. .779 .729 .667 .617 .550 .410
Cylinder Bore .000 - .779 .000 - .729 .000 - .667 .000 - .617 .000 - .550 .000 - .410
Skeet I .005 - .774 .005 - .724 .004 - .663 .004 - .613 .003 - .547 .002 - .408
Improved Cyl. .010 - .769 .009 - .720 .007 - .660 .006 - .611 .005 - .545 .004 - .406
Skeet II .015 - .764 0.12 - .717 .010 - .657 .009 - .608 .007 - .543 .006 - .404
Modified .020 - .759 0.19 - .710 .015 - .652 .014 - .603 .012 - .538 .008 - .402
Improved Mod. .025 - .754 .025 - .704 .020 - .647 .019 - .598 .016 - .534 .011 - .399
Full Choke .035 - .744 .035 - .694 .028 - .639 .025 - .592 .022 - .528 .015 - .395
Extra Full .040 - .739 .040 - .689 .035 - .632 .027 - .590 .024 - .526 .021 - .389




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