If there were an urban myth that suburban homes are impervious to becoming cannon fodder, it just got busted.

Two homes, a sidewalk and a van all took fire after a test for the show MythBusters went awry Tuesday and sent a cannonball out of a bomb range and into a nearby residential neighborhood in Dublin, California.

The cannonball, which took an unexpected bounce off a safety berm during the test, traveled 700 yards outside of the Alameda County Sheriff’s Department bomb range where it was fired, hit a sidewalk, crashed through the front door of a home, traveled upstairs and went through the...