Bore Diameters
Bore diameters vary from
manufacturer to manufacturer,
but the Small
Arms & Ammunition Manufacturers Institute (SAAMI)
does issue a recommended
standard dimension for each gauge. These and the amount of
choke constriction
per designation is as follows:
This chart covers internal
diameters
Gauge |
Bore
(inch) |
Full
Choke
(inch) |
Modified
Choke
(inch) |
Imp-Cyl
Choke
(inch) |
|
12 |
.729 |
.694 |
.710 |
.720 |
|
16 |
.667 |
.639 |
.652 |
.660 |
|
20 |
.617 |
.592 |
.603 |
.610 |
|
28 |
.550 |
.528 |
.538 |
.545 |
|
.410 |
.410 |
.393 |
.402 |
.406 |
Cylinder choke would of course be exactly the same as the
bore diameter per gauge. |
This chart covers each of the chokes in the amount of
constriction
Gauge |
Bore
(inch) |
Full
Choke
(inch) |
Modified
Choke
(inch) |
Imp-Cyl
Choke
(inch) |
12 |
.729 |
.035 |
.019 |
.009 |
16 |
.667 |
.028 |
.015 |
.007 |
20 |
.617 |
.025 |
.014 |
.007 |
28 |
.550 |
.022 |
.012 |
.005 |
.410 |
.410 |
.017 |
.008 |
.004 |
Cylinder choke has no constriction and is the same as the
bore in diameter.
-- From Shotgun Gunsmithing
by
Walker, a Gun Digest
Book. P 157-158.
