Thanks for the explanation.
Let's see if I am following this.
If the round was certainly designed to burst within the barrel, it would have been made of flimsy material.
Cannister was in a tin case, so it was not made of flimsy material. There is some doubt as to whether it burst inside the barrel or outside the barrel, or what indeed the intention was.
Cannister had a much longer range than grapeshot, so there has to be an explanation for this.
If the cannister round burst immediately on leaving the barrel, then that would hardly explain a massive increase in range. Right so far?
Would the logical conclusion be that the tin case burst elsewhere, presumably when met with sufficient force for it to do so? Would it be presumptious of me to assume that hitting a hard object like the ground would be the sufficient force?
Am I being obtuse or is there something I have missed here? Is it really that simple?