[poobear]

Yep, sounds like a the Pawns Stars misfired! :)

[Red Badger]

The Myth Busters did that once:

http://www.youtube.com/watch?v=ui-xBeqBNi4

http://www.cnet.com/news/mythbusters-make-apologetic-house-call-after-cannon-accident/

[Ozark Tom]

http://pleasantonweekly.com/news/2012/06/27/mythbusters-to-resume-testing-experiments-after-cannonball-mishap-