Not a duplicate of that, that's a visual bug (at least, in my tests of it). The video in the comments for that bug, however, is the same bug.
It may be worth noting that the cannon was originally built in 13w01a (At least, that's the version I remember building it in)
http://www.youtube.com/watch?v=EDJ7fNwK3L0 demonstration of the glitch
You have to have your inventory open
Not a duplicate of that, that's a visual bug (at least, in my tests of it). The video in the comments for that bug, however, is the same bug.