Just found this video of a Mountain Bike "BadAsslon" held in Lanesboro, MA this weekend. They could use some work on their gun handling and range rules, but looks like fun. My apologies for the "end" of the video ahead of time.
http://www.youtube.com/watch?v=jtnpOD9ifq8
http://www.youtube.com/watch?v=jtnpOD9ifq8