All the manufacturers use their own type of powder. The flash that you saw today was unburned powder lighting off outside the end of the barrel. The different types of powder used burn at different rates, some burn faster than others. Barrel length also has some to do with it, shorter barrels will usually get muzzle flash when longer ones don't. Hope this helps. Muzzle flash shouldn't really matter, except when picking a defensive round to use in the house. You don't want to blind yourself if you ever have to use it indoors(hope you never have to) I hope this answers your ?

Winchester white box ammo is pretty dirty stuff as in it leaves a lot of ash behind in the pistol. What he said about muzzle flash.

What people talk about when talking about dirtier powder is what's left behind after the shot. The dirtier the power the more crap in your weapon to clean out or gun up the works. The flash you noticed could have been due to a few variables. The lighting conditions during your shooting being one of the main ones. some powder burns faster than others and some powders are designed to have less muzzle flash.

All powders will have some muzzle flash. This link might help explain it all a little better than I can.