I may be way off in my thinking, but I would think barrel length would play a role in your powder choice. Maybe JB, Aussie or one of the other writers will chime in.
Seems to me that if you had a shorter barrel a faster burning powder would be benificial. Again, im only guessing, but you want all the powder to be burned before the bullet leaves the barrel. If you had a slow burning powder that was effecently being burned in a 24 or 26 inch barrel, it might not all be burned at the 20 inch mark. Thus causing excessive muzzleflash, which I would say doesnt hurt anything, but may be leaving FPS on the table. Were if you burned a powder that was effecently burned at the 20 inch mark then you would be wringing all the FPS available. I may be wrong in my understanding of powder performance.
