I read in an account of the 101st 'Screaming Eagles' paratroops in Normandy and France that their gunpowders were less efficent than the German equivalents - ie; the German gunpowders were smokeless and flashless, whereas the American ones left a cloud of smoke, often betraying where the firing was coming from.
In a DVD on the Panzer V in the same thing is mentioned - Panthers were often hard to detect in ambush situations because their 75mm showed little flash and smoke when fired.
Has anyone else come across similar comments?
For modellers I wonder whether that means that on larger American weapons, especially, there would have been a build up of powder residues around the muzzle?

Just a thought...