Maybe a little more vel. or Range, I dont think I would care for the looks of the can flush with the end of the barrel, Just like long barrels, all my custom made B.P. Southernmountain rifles have 48 in. barrels.- Joe
But this isn't a cannon, it's a mortar it lobs. Range is increased by increasing powder charge. You really don't want more velocity on a mortar any way, you can't see the ball go down range. A can doesn't take advantage of higher velocity any way as it tends to tumble all over the place, if it doesn't self destruct right out of the barrel. The increase is velocity in smoothbore can mortar will be marginal anyway as the bore riding section is a expansion chamber and the powder chamber is fixed dimensions. You can only get so much powder in there
If you need to cover the range between mortar and a cannon make a howitzer. A howitzer will get you high angle lobs and low flat trajectory....and a third gun!!! Mortar for close work, howitzer for mid range, cannon for longer work
As long as the can is below the muzzle what's the problem?
And, I want to see the Mountain rifle also.