Originally Posted by Philip
The size differential [between European and Moroccan flasks] could be due to the necessity of [the latter] using more powder in a load when the powder was weak. There exists a 1916 report by a French intelligence officer identified as Capt. Delhomme, entitled "Les armes dans le Sous Occidental" which describes the armament used by tribal peoples in Morocco, and his comments on gunpowder are interesting. Dehomme noted that powder was manufactured at various locales and that its quality was not consistent. The quality varied considerably from here to there. The overall market seemed to be rife with shoddy product made from inferior or adulterated materials, such as unrefined sulfur or sugar carbon (instead of proper charcoal). Powder made from the latter was weak and unstable, losing whatever potency it had after a couple months.
The report, in English summary, can be read in S. James Gooding's article "The Snaphance Muskets of al-Maghreb al-Aqsa" in the journal Arms Collecting, Vol 34, No. 3, pp 87-93.
The vagaries of unreliable supplies of good powder may also explain the preference for very long barrels, since the poor stuff was likely to be much slower-burning and thus it would be advantageous for the bullet to remain confined a bit longer to allow sufficient combustion pressure to build before it left the muzzle. Likewise the tendency of native firearms in some tropical areas to have excessively long barrels (by Western standards) due to the moisture-absorbing nature of the charcoal in gunpowder, affecting its performance in humid climates.