"GLOCKs came originally in 9mm, and have also been made in various numbers in 10mm, .40S&W, .380, 9X21mm, .357 Sig and .45 GAP. However, the only acceptable caliber for a man to carry is .45 ACP. 10mm is good but hard to find, .40S&W is a wussified 10mm that the FBI created when it found out...