Turn the clock back 150 years, to a time when frontier disputes in Colorado were often settled with a six-shooter or a rifle. In remote areas of the state the judicial system was weak or unorganized. That’s the era Kenneth Jessen lays out for Colorado Matters, talking about his new book “Frontier Colorado Gunfights.” In the book, he tells 31 true stories of frontier Colorado gunfights, with big names like Doc Holliday, Jesse James, Clay Allison all doing battle here.