A question has occurred to me concerning the use of black powder related to its use in pyrotechnics and firearms.
Why, as per specifications related to pyrotechnic black powder rocket construction and the loads for a primitive firearm, are there references to the specific grain size that should be utilized, i.e. : Fg, FFg, FFFg ?
The fundamental burn characteristics of these separate (uncompressed) powders is understood…
My confusion is derived from the fact that when one “rams” the powder, whether in a black powder rocket, or a primitive firearm, the original grain size is destroyed, resulting in a new, uniform, “grain” that is characterized by the compartment it has been packed into. So what makes the difference what size grain one starts out with?