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Dr 16g and I spent part of our first evening in Russell measuring chambers and bores and choke constrictions and as is usual, found some surprises. Once again, a bore micrometer is a very good investments when messing with old SxSs.

Jes guys what's wrong with just patterning the gun and finding the loads that work. If it kills in front and cripples behind it must be good Twisted Evil

Good luck to all and a very Merry Christmas!!

*Last edited by revdocdrew on Mon Oct 29, 2007 9:09 am; edited 1 time in total*

The chokes of all 3 of Dr 16g's guns were tighter than expected and the LC bore was .660.

I previously used the excellent but expensive Stan Baker, now the CSP Barrel Reader, available from Shotgun Sports magazine 800-676-8920
I'm now using Skeet's Bore Gauge from Brownells www.brownells.com for only $91. Zero with the supplied .700 ring. Standard 16 is .662-.665.
The tool is easy to use, just be sure the bore is clean and re-zero every time you take a measurement.

Member Joined: 26 Apr 2005 Posts: 743

If you're buying a gun, it's kinda nice to know approximately what the chokes are before you get out the plastic or write the check. For example, if you stick your bore and choke gauge in the barrel and discover it doesn't have any choke, that might not be the gun you want for pheasants--although it might be just fine for grouse & woodcock. And it's also nice to know in advance if you're going to have to pay another $100 or so to have both barrels opened.

I've put a bore gauge into a bunch of 16's, and I've found some with bores as tight as 650; don't think I've ever found any as overbored as 670. And that's the problem, of course, with a tool like Galazan's choke gauge--which is all I usually carry at gun shows. If the bore isn't very close to standard diameter, then you can get a choke reading that's way off.

The Miroku choke nomeclature:

+ full choke
++- improved modified
+- modified
++ improved cylinder
SS skeet
CYL cylinder

Member Joined: 31 Oct 2005 Posts: 446 Location: Wisconsin

Thread updated

Courtesy of chorizo

The following is a generally agreed upon list of 16 ga shotgun TRUE BORE DIAMETERS (NON-BACKBORED BARRELS) and a listing of generally accepted choke constrictions (IN THOUSANDS OF AN INCH) noted prior to the choke diameter.
Gauge 16
True Bore Dia. .667
Cylinder Bore .000 - .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

Also please note that variances of .002 (I have been told) are not uncommon as it is difficult to bore to exact measurements.

Courtesy of Citori_16

16 gauge Browning Invector barrels measure 0.667" =/-0.0015"

Full = 0.624" or 0.043" constriction
Imp. Mod. = 0.643" or 0.024"constriction
Mod. = 0.657 or 0.010" constriction
Imp. Cyl. = 0.661" or 0.006" constriction
Skeet = 0.665" or 0.002" constriction
Cyl. = 0.673" or +0.006" constriction

Trulock Precision Hunter Chokes for Browning Invector Barrels:

Based on a 0.670" bore which they figure to be +/- 0.002" from nominal bore spec, but not with all manufacturers. In this case they would be +/- 0.003" from Brownings spec of 0.667" nominal bore diameter.

Cyl. = 0.670 or 0.000" constriction
Skeet 1 = 0.675 or 0.005" constriction
Imp. Cyl. = 0.680 or 0.010" constriction
Skeet 2 = 0.685 or 0.015" constriction
Mod = 0.690 or 0.020" constriction
Imp. Mod = 0.695" or 0.025" constriction
Full = .700" or 0.030" constriction
Extra Full = 0.710" or 0.040" constriction
Turkey = 0.730" or 0.060" constriction
Turkey = 0.740" or 0.070" constriction

choke constriction tolerance +/- 0.001"