I found where the author of the book "The Art of Wing Shooting" Leffingwell, got the idea that modified chokes were five thousandths constricted. In the chapter on chokes he refered frequently to Greener. I looked in the book "The Gun and it's Developement" In the chapter on choke boring, he writes..."To an English gunmaker the terms (choke boring) mean simply "barrels whereof the diameter of the bore at the muzzle is less than the bore at some point behind the muzzle, other than the chamber," while any gun-barrel constricted at the muzzle to the extent of 5,000ths of an inch may be termed a modified choke." He goes further and writes..."A full choke is constricted to the extent of 30 to 40,000ths of an inch." This makes more sense. It seems Leffingwell was quoting Greener and maybe he wasn't very well informed, but then choke boring was new and maybe a lot of writers wern't fully knowledgable.
Pete
