Jezzails are the most reliable weapons developed by Clan Skryre (they're almost safe!). For each Jezzail that obtains a result of 1. on its roll to hit, roll another dice. If this second dice rolls a 2-6 the shot was a dud and all is fine, but if the result is a 1 the gun has a serious problem. To represent this, the Jezzail hits itself (roll to wound as normal).