At what temp. does black powder burn when fired? Does quanity or size affect the temp. ? I am looking to refinish an old ww2 line throwing cannon and searching for a suitible coating that will withstand the temp.
Black powder burns slower the larger the granule but its all over in about 2-5 thousandths of a second so no significant heat transference has time to take place between the burning powder and the thick metalwork around it. Maybe it might feel a little warmer to the touch but that would the extent of it.
The heating effect in modern rifle barrels is due almost entirely to bullet friction which can be significant if multiple rounds are fired but that won’t be the case with a line thrower. I doubt that you would notice any heating at all.