Why did the Mythbusters' cannonball fly so far?

http://www.wired.com/wiredscience/2011/12/cannon-balls-size-matters/

Map
http://www.wired.com/underwire/2011/12/mythbusters-cannonball-map/

Mythbusters says "Safety protocol followed" on set that shot cannonball into a house & a van

http://dublin.patch.com/articles/mythbusters-tv-show-filming-may-be-source-of-explosion