Finally someone has seen the problem. Cannister had different constructions. Much of the comments from me has been upon French cannister and was distinct from that of British case shot and Austrian cannister etc...
All I have been trying to explain is that the explanation that has been taken has been for British constructed cannister as given by Hughes and others. It is to look at the construction.
The concept of rupture is to punch a hole in the top of the cannister. This seems unlikely with the thickness of the French cannister as the gauge was over 1/4" tin. Now the opening up of the top or along the seam seems more likely.
Also when looking at ballistic stability. Something that is over four time its length than its diameter will fly straight whereas less than this it is likely to spin in the air. Addition of fins makes this shorter and adding spin from rifling. This is the reason for the stick on the Congreve rocket.