Thank you Jim and Michael
,
for your input. I can see that an artillery piece with 'portability' would have great tactical advantages in certain terrain or for rapid deployment during phases of a battle.
The cannon on 'Mythbusters' was not historically accurate ie dimensions etc. However the construction was fairly close. It was used to fire a solid ball and was compared to an iron barrelled cannon with the same 'bore'. As I said before interestingly the muzzle velocity was greater with the Swedish cannon. (I believe the powder charge was the same for both cannons). Unfortunately the 'breach' end was blown out and therefore was only fired once.
I suspect that, perhaps, the breach end was either incorrectly made or they had reproduced an earlier version (which was later modified).
Even with the overheating problem they still seem that they would be reasonably effective. I would think that if a smaller charge was used to propel grape shot it could have been a useful 'anti-personnel' weapon. Even if the copper barrel was slightly deformed by the heat ....grape shot would still exit....a full cannon ball might not with the obvious consequences
Quick moving artillery would be a massive advantage during a battle....perhaps if the Swedes had utilised this cannon as a large 'shotgun' ...it may have proved its worth
Summary from Mythbusters...........
"... For comparison, the Build Team fired a Civil War Parrott gun of similar size to the cannons described in the myth to measure its muzzle velocity, which was 389 mph (626 km/h). Because there are two separate versions of the myth, originating from Sweden and Ireland, the Build Team decided to test both designs. The Swedish cannon consisted of a copper core wrapped in leather and iron bands, while the Irish cannon was built completely out of leather. The Swedish cannon managed to fire its cannonball at a speed of 450 mph (720 km/h), but blew out its breech in the process. The Irish cannon failed spectacularly, with the breech blowing out, the cannonball moving only two feet, and the barrel completely unravelling, making a second shot impossible. They then built a third leather cannon and reinforced it with significantly more leather. They also lubricated the barrel to make it easier for the cannonball to fire. The cannon managed to fire successfully, but the cannonball could only achieve a speed of 52 mph (84 km/h). While the cannon was still structurally intact, the barrel was too damaged for a second shot......."
Kind Regards David