No offence meant. Just one of my moments of attempted humour
The humor part of it blew right over my head. I am rebuilding an old wooden door on the front of our house and I was taking a break figuring out my next move on the door. Age catching up with my mind. Can no longer run two trains on a one-track mind.
Mad Monk
While talking of powder. I ran across another "shoot over sbow" thing on another sight. This time concerning 18th c LRs. I wonder if the non-press cake powder would not get crushed to near dust as the powder at the rear burned and put pressure on the front of the charge? This would make finding "unburned" grains even more unlikely.
Dan
Back when I was into looking at how the "gunpowder" technology evolved I made several batches of powder the way it had been done before the introduction of the wheel mill and powder press.
The finished grains looked like small stream pebbles. Well rounded. It then hit me how the English came to call some of their powder "pebble" powder.
The grains were unique. The interior portions of the grains were low in density and not "consolidated" all that well. Meaning the interior of the grains lacked the degree of mechanical strength seen in pressed powder grains. The exterior of the grains had a thick very hard shell that was very smooth and glossy. Looking as if each grain had been dipped in molten glass. I then suspected that this visual appearance is why powders were then described as being glazed. As in glass.
If you ignited these grains in the open air they would at first burn very slowly because of the hard glaze and the excess of potassium nitrate forming that glaze. Then once they burned through the glaze they burned almost explosively. With the press densification of black powder powder the pressing, compacting and consolidation of the mass acts to reduce burn rates and give the powder grains a more controlled uniform burn rate from the surface until they were completely consumed. This is important in pressure development in the gun.
I have looked at that shoot over snow or a white sheet in the past. According to Nobel &Abel the powder charge is totally consumed before the ball has traveled more than a few inches in the barrel. Before George Rummmel passed away he had sent me some calculations on that. A charge of 3f would be consumed after the ball has traveled about 3 inches in the bore. A charge of 2f would be consumed around 5 to 6 inches.
What I did find that a lot of what looked like unburned grains were simply balls of powder combustion debris ejected from the bore with the gasses behind the projectile.
I had also noted that certain patch or bullet lubes will get into some of the powder grains and cause them to burn only slowly. They will go out the muzzle streaming smoke. If you don't swab between shots and pour a charge down a dirty bore some grains will hang in the bore fouling. Then when you run the patched ball down the bore these grains are mixed in with the fouling from the previous shot that gets packed on top of the fresh charge. They may also end up not burning as rapidly as that in the charge.
When I had looked at the powder that was not press densified and how it burned in two stages I though about the soft wrought iron barrels and how that related to rapid bore wear in the breech section of the gun. Especially in the big .69 caliber military muskets such as the Brown Bess.
Mad Monk