If the fire arm is in good condition ( any doubts, have it checked by a gunsmith ), 38 S&W would be the proper cartridge. Note, just in case you are not aware of the difference, Not 38 Special, at the time many of these old revolvers were made, the cylinders were drilled with out a " step" and in some of the old revolvers .38 Special will chamber, Very, very bad Karma.