Weighing projectiles?

[Mr. 16 gauge]

For those of you who are "runnin' ball" and casting your own projectiles: Do you weigh each individual ball or conical to check for consistancy? I've been doing it with my regular conventional bullets since I started casting, and been doing it with my muzzleloader projectiles for a number of years now.....I thought I need not bother, since they were cast out of pure lead, but I have found some large discrepancies in various lots....not sure if it is impurities, air cavities, or whatever, but they are there. I try and keep all projectiles (modern & black powder) within a grain or two; all the rest go into the scrap box to be recast.
Anyone else find something similar?