I know it is the measurement of the barrel from land to land, but one could say 9mm for a 9 millimeter and "40 caliber" for a .40. My question is what is .40 or .45 of? an inch? because if I remember correctly a .40 is 10mm right? I took a gun permit class yesterday and my instructor didn't know what the ".40" is a measurement of.
9 years 33 weeks ago, 8:45 AM