You might or might not find substantial variation in diameter of the shot, depending on your source and even the run. I don't know much about the manufacturing techniques - i.e., if the material is molded, swaged, dropped or some other method, but there are a boatload of variables (temp, composition of the lead, etc.) which could effect the diameter.
I suspect that the only way to find out is to buy some and test it. Ballistic Products lists their 00 1/2 shot at $36.90 for an 8 lb. jar, with UPS FedEx charging their customary pound of flesh. Hornady buckshot is .350, claims to be swaged to a tolerance of =/- .001", and runs (according to their website) $33.92 a five pound box. Since a 000 pellet weighs about 70 grains, you should get about one hundred per pound, so your Ballistic Products shot comes to about $.0046 per shot, or about $.00678 for the Hornady.
Hmmm...