As to the weighing vs measuring argument - powder energy is a function of the mass of the powder, not the volume dispensed, and most powder measures dispense by volume. Dispensing without weighing can sometimes be as accurate, but weighing is never less accurate. If someone claims it is, their test was flawed or the sample size was too small.
This is an oversimplification. Unless treated with a waterproof coating, modern smokeless powder is hygroscopic so its energy density and its mass density are both functions of its exposure to humidity. Its macroscopic volume, however, is not dependent on exposure to humidity.
