The Firing Line Forums - View Single Post - New Mossberg 12 Gauge Bore Diameter: .733"

TrumpetShooter · December 8, 2010, 12:48 PM

I just bought a new Mossberg 500 12 gauge shotgun, with a 28 inch ported field barrel with screw-in choke tubes. I measured the bore, and it is .733 inch. The advertised bore diameter is .731 inch, which is .002 inch over the so-called "standard" measurement of .729 inch. I checked my gauge, and it appears to be accurate. (For example, I measured a Carlson's modified choke with an advertised inside diameter of .710 inch, and my gauge was right on.)

Also, the factory Mossberg choke tubes measure larger diameters than standard choke tubes, based on Carlson's, Turlock, and other choke charts. The larger choke diameters put them very close to the correct constrictions for their respective choke designations, although a bit more open than they should be. I have not patterned the gun, but it converts clay targets to dust at 15 to 35 yards with IC, Mod, or Full chokes.

I wonder if this is a recent phenomenon, or if Mossberg 500 bores have always been slightly over-sized. Do any of you know? Have any of you measured the bore diameter of a Mossberg 500 12 gauge field barrel? I am especially interested in the bore diameters of older Mossberg 500s. It would be interesting to know the bore diameters of other shotguns, as well.

December 8, 2010, 12:48 PM	#1
TrumpetShooter Member Join Date: December 1, 2004 Posts: 42	New Mossberg 12 Gauge Bore Diameter: .733" I just bought a new Mossberg 500 12 gauge shotgun, with a 28 inch ported field barrel with screw-in choke tubes. I measured the bore, and it is .733 inch. The advertised bore diameter is .731 inch, which is .002 inch over the so-called "standard" measurement of .729 inch. I checked my gauge, and it appears to be accurate. (For example, I measured a Carlson's modified choke with an advertised inside diameter of .710 inch, and my gauge was right on.) Also, the factory Mossberg choke tubes measure larger diameters than standard choke tubes, based on Carlson's, Turlock, and other choke charts. The larger choke diameters put them very close to the correct constrictions for their respective choke designations, although a bit more open than they should be. I have not patterned the gun, but it converts clay targets to dust at 15 to 35 yards with IC, Mod, or Full chokes. I wonder if this is a recent phenomenon, or if Mossberg 500 bores have always been slightly over-sized. Do any of you know? Have any of you measured the bore diameter of a Mossberg 500 12 gauge field barrel? I am especially interested in the bore diameters of older Mossberg 500s. It would be interesting to know the bore diameters of other shotguns, as well.