According to my (Rather Old) Machinery's Handbook they give the weight of lead @ 707.7 lbs per cubic foot. Using this figure a one lb ball would have a diameter of 1.670701 to six decimal places. This would make;
12 ga = .730"
16 ga = .663"
20 ga = .615"
28 ga = .550"
Thus two sizes show .001" larger than the charts, two remain unchanged. Some other gauges could grow by from .001"-.002" while many would stay the same, none would "Shrink" as the base for calculating (1 gauge) is larger by 1.416".
This is probably more than anyone wanted to know, but this is the Nitty Gritty in a Nutshell on gauge sizes.
