12 GA
the buddy worked good but it was hard to push it through the barrel straight - I have a rod for cleaning the barrel - not sure if I need an attachment. From BarrelBuddy Customer Care Team: Hello Kevin, First, thank you for reviewing the BarrelBuddy 12G size. We appreciate you taking the time to do that! You had an issue keeping the BarrelBuddy straight on the rod. To avoid this, you should use the proper size JAG attachment (12G), which will provide a larger surface than the rod itself to push the BarrelBuddy through. Hope this helps! Blessings, BarrelBuddy Customer Care Team