How is the caliber of a rifle or handgun determined? A, The length of the barrel measured from the muzzle to the action A, The length of the barrel measured from the muzzle to the action The length of the barrel measured from the muzzle to the action B, The distance between opposite lands inside the barrel B, The distance between opposite lands inside the barrel The distance between opposite lands inside the barrel C, The circumference of the barrel when measured from the exterior. C, The circumference of the barrel when measured from the exterior. The circumference of the barrel when measured from the exterior. D, The length of the ammunition that it can fire D, The length of the ammunition that it can fire The length of the ammunition that it can fire