George, the plug gauge will not tell you what you claim it will. Sorry.
Looks like I'm universally out-voted on this one. Oh well, I keep on learning.
However, I wonder how many of the guns I see and "measure" with my Galazon guage have really been reamed out to such an extent that I can't even tell open choke from tight. I think maybe not so many.
Whenever I buy a gun or if a seller will let me shoot it, I find a refrigerator or washing machine box behind a store and carry it out to the woods and shoot it. It seems to me that the choke comes out about what I measured on most of'em...Geo
