I don't believe a C&B gun has enough length of compression to ever approach the temperatures required by dieseling.
When I read the Bevel Brothers article about their experiments with dieseling, my first thought was, "They are using a short (about 12 inch as I remember) barrel. That won't give the results they are looking for" and indeed, it only fired a few times.
Dieseling depends on compression to generate heat.
In a modern engine, the compression ratio is about 20:1.
Putting this into prospective, that would be similar to compressing a 20 inch long air column to 1 inch.
It is quite obvoius to me that when ramming a patched ball down a 42 inch barrel over a powder charge which is only about 2 inches tall, a compression of 21:1 is possible if there are no air leaks.
Of course, this would take a great deal of force to acomplish rapidly but a 20:1 compression is not necessary to ignite black powder.
If done rapidly, just compressing air to about 100 pounds per square inch will raise the air temperature to about 800 degrees F., more than adaquate to ignite real gunpowder.
This pressure only requires a compression ratio of about 7:1.
I might also mention something about speed.
If the ramming of the patched ball is done slowly, much of the heat generated by the compression will be absorbed by the walls of the barrel. Also, much of the air pressure will be lost due to leakage at the nipple/vent and around the patch.
How much ramrod force would it take to generate 100 PSI of air pressure? That depends on the caliber, but if a .50 caliber patched ball were being used, it would be (.50/2)E2(Pi)(100) = 19.63 pounds.
For a .45 caliber patched ball it would be (.45/2)E2(Pi)(100) =15.90 pounds.
Both of these figures would be in addition to the force to drive the patched ball down the tight bore and are higher than most of us would ever use, but for someone who is in a hurry and unaware of the potential for disaster, it is possible.
I think the reason we don't see more of this sort of occurance is because most (if not all) of us take our time ramming the patched ball down the barrel, often doing this in short 6-10 inch steps and many of us make a point of keeping the vent open during loading.
:m2c: