In the continuing quest to eliminate muzzle flash for my SD loads (can't hit what you cannot see if you're blinded by the flash) I came across this article. http://findarticles.com/p/articles/mi_m0BTT/is_190_31/ai_n27380935/pg_5/?tag=content;col1 From American Handgunner, Dec 2007. I'd always assumed that faster burning powders produce less or no flash. Universal Clays produced NO flash while a faster burning powder like Bullseye, did. On a burn rate chart, fastest to slowest, Bullseye is #6, Unique (both widely used by me) is #35. Universal Clays comes in #16th, slower burning than my old, faithful Bullseye. I posted on this topic a few weeks ago but information on this topic is hard to find in any quantifiable form. My loading data shows many loads for Universal Clays with a variety of bullet weights in 9mm and 45 ACP, my SD calibers of choice (or default......it's what I own). Guess I'll buy a pound, load some rounds, use my wife as an unbiased observer and see what I can discover. I think this is an important topic for those of us who are serious about what we use for SD loads since most unpleasant encounters with BG's happen at night!