Originally Posted by Jim McDougall
Thanks Fernando, indeed Philip very well explained the dynamics of gunpowder, and I had often heard that flintlocks often burst due to improper charge and just the kind of detonation you describe. I think the terminology is confusing, I had read that detonation or explosion were wrong terms.
I suppose that explosion might be regarded as a concentrated and VERY rapidly burning of a measure of gunpowder (which they says is called 'black' powder, yet according to sources they say is gray). Confusing.
Jim -- you have it pegged. The impression I get from the literature and being a layman taking advice from shooters who reload their own cartridges, is this: burning (combusion) and explosion (or detonation) are on the same spectrum, and one becomes the other when the speed of heat- or flame induced chemical change passes a certain point.
And confinement does play a huge part. Both black and smokeless powder will burn with a flame in open air but will go boom when in an enclosed space. The cartridge guys emphasize that modern smokeless powders are more powerful than black powder (plus the advantages of far less flame, smoke, and residue) to a large degree because the combustion "profile" is different, mainly faster (not being a chemist I can't delve further into the theoretical details) and the fact that the constituent chemicals generate more "oomph" in the first place. But the fact that my head is still intact is that I followed their advice to NEVER load smokeless powder into a barrel or a cartridge case designed for a black powder gun. Also to be careful to choose the correct type among the plethora of nitrocellulose powders on the market for a particular caliber and type of firearm, because burning rate varies to measurable degrees from one to another and an inappropriate burning rate can create dangerous chamber pressures that might damage either the weapon or the guy firing it.
From this, may I clarify the comment on overloading, that it isn't just flintlocks that are in danger of bursting under excessive charges, this is true of all firearms including modern ones. Nowadays, barrels of modern ordnance steels are generally of a high level of strength and safety, but it is the breech components that can still fail and turn into shrapnel (I've seen it happen on rifle ranges and it's scary, lucky that no serious injuries resulted). Back in the era which we are talking about, quality of gun barrels varied enormously -- this was true until industrial processes and government "proof" standards were more systematic. The difference between the best sporting gun barrels, those wonderful creations by the Cominazzo family or by Bis and the best Spanish makers, was far and away above the typical munition-quality barrel, which was typically made of a longitudinal flat strip of iron, curled lengthwise around a mandrel, with a single seam hammer-forged straight from breech to muzzle.