I think it is a misnomer to say this powder burns dirty, or that powder burns clean. The truth is that any powder will vary in how completely and cleanly it burns, in direct relation to how closely it is loaded to its intended purpose. The generalization that ball powders burn dirty is flawed. Ball or extruded powders will burn dirty if you use a slow powder in a light pressure load.
Slower powders need more pressure to burn fully. I have some super slow WC872. If I load it straight in 308 or 223, it leaves a trail of partially burned grains down the barrel. However, in a 20mm application for which this powder was designed and intended, it burns cleanly enough to sustain very rapid rates of fire. I have tested duplex loads, using two powders in one cartridge, and was able to make WC872 burn more cleanly and completely in these calibers. Also, using the heaviest available bullet will help slow powders burn more completely, too. Conversely, using too fast a powder will cause higher than safe pressures. It is not the powders fault, if you selected the wrong powder for your load.
Rather than blame a powder, I believe the reloader should consider how suited the powder is for the load they choose to load. If you select the right powder, for the right load, in the first place, you won't be blaming a powder for burning dirty, IMO.
Last edited by Marco Califo; November 28, 2012 at 08:00 PM.