Welcome to the forums from the Wiregrass! In my area, the big box sporting goods stores all carry .38 S&W. You shouldn't have any problems finding it. The .38 S&W was originally loaded with black powder. When smokeless powder became available, the ammo manufacturers made sure the energy in the cartridges didn't change so the abundant (at the time) black powder guns could use it. Your Perfected was made after most S&W guns were easily digesting smokeless loads. It should be fine with standard load commercial ammo.

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Guy
SWHF #474 SWCA LM#2629