What is the rifling depth on a .40 caliber Southern Mountain Rifle?On a .40 caliber Southern Mountain Rifle, the rifling depth is 0.01 to 0.02 inch. Category: Parts & ComponentsLast verified: 2026-07-25Also called: gun, rifle, muzzleloader, muzzle loader, firearm, southern mountain, SMR, poor boy More in Frequently Asked Questions