Join Date: Dec 2004
A fine acquisition, the patina on the metal is impressive. The recessed touch-hole is interesting, am wondering if it has been "bushed" or lined to reduce its diameter after being eroded after extensive firing. At any rate, the fact that there is a deliberately-made "crater" around it leads me to think that here we have the first steps toward the development of the priming-pan, to make ignition faster and more sure with the slow-match.
As far as the thickness of metal behind the bore, maybe Michael or another forumite who has examined far more European handgonnes than I have can comment. I can only suggest that such a thick breechplug be looked at in light of the rapid evolution of gunpowder technology at the time, and the understanding of chamber pressures must have been limited considering the variability in powder composition and granulation. A bit of "over-engineering" certainly wouldn't hurt!
The late Dr. Joseph Needham of Cambridge University, in Vol. V part 7 of his monumental SCI. AND CIVILIZ. IN CHINA (Cambridge, 1986) presents interesting data on gunpowder composition and manufacture in the West, the Near East, and China during the late medieval period until ca. 1700. He cites two factors influencing the increase of gunpowder's efficiency as an explosive propellant: the increasing proportion of saltpeter (potassium nitrate) relative to sulfur and carbon in the formula, and the introduction of "corning", i.e. the manufacture of powder in granules as opposed to a flour-like powder. A comparison of surviving European formulae show a rise in average nitrate content from about 33% at the beginning of the 14th cent. to something very near the modern theoretical 75% which was already known by the second half of the 17th. A graph on page 349 of Needham's book shows that by 1400, the typical gunpowder used in firearms contained about 40% saltpeter; the figure had risen to about 55% a century later.
The corning or granulation of powder probably dates from ca. 1450, in Nuernberg. Corned powder allows for more efficient combustion because of the air spaces between the grains that exist even after the charge is tamped home with a rammer. More explosive energy to push the projectile out of the barrel also means greater pressures inside the bore during firing, however. The French traveler J. Tavernier two centuries later that mills in Vietnam and Thailand were making powder whose grains were in the form of "little rods" -- a very modern concept which has been common in the West only since nitrocellulose ("smokeless") powders supplanted black powder in the last 120-odd years. Tavernier regarded this rod-granule powder as superior to anything known in Christendom.