I carried a S&W Model 19 from 63-66 with MACV. We were working with "Company" types and could get any kind of ammo we wanted. I wasn't issued a pistol (carried a scoped Winchester Model 70)so there was no restriction or issue of handgun type. It had a 4" barrel and I carried it in the standard issue shoulder holster for the 1911. I bought the pistol in the Exchange in Saigon.I never fired it(or even drew it!) in combat and brought it back to States with me when I rotated. Regretfully I sold it years later.