Pyrotechnicians make much of their blackpowder and conduct contests to see whose is the strongest or best for various effects. In the forum I am on, charcoal seems to be the key and many woods and methods to char them have been tried. Of course milling, corning, glazing, and screening are also important.
When I was a serious competitor in m/l rifle competition I screened every bit of the black I used in matches. I had two screens that it went through. One sifted out the very large kernels by not letting them pass through. Then I took what passed through and sifted it through another finer mesh that allowed the fines to pass through and retained the "medium" sized particles. The very coarse stuff was used for in my shotgun, the very fine was either discarded or given to someone who shot flint. I got very consistent velocities with this sifted powder, usually Dupont GOEX. I have a 14 lb., .45 cal. roundball longrifle (buffalo gun, for those of you who know what that is), that I built, that will shoot 5/8" five shot groups at 100 yds. on a good day. I attribute part of that to the sifted powder.
Screening by the user, for a shotgun, is worse than useless, IMO. It's a total waste of time. I do understand that the poster was referring to screening at the manufacturing facility, before packaging and shipping, but in reality they do not do a very good job of it. There are particles of extremely varying size in a can of black.
SRH
