[Ancesthntr]

Any idea what the bore diameter of 10 and 12 guage shotguns are?

I believe that a 12 gauge shotgun is .71 cal. I don't know about a 10 gauge, but it is certainly larger.

[Ancesthntr]

From the Shotguns board over at The Firing Line:

"28 gage - .550, 20 - .615, 16 - .662, 12 -.729, 10 - .775. 410 is of course .410"