I am assuming you mean one in a serious caliber? .22's out of the picture? my smallest 6 shot is a Smith M-65. .357 mag. 3" barrel. Round butt. Carries well. Shoots great.
Why 6 shots? The smallest practical defense revolvers are the Smith & Wesson J-frames, and those are all 5-shooters--except the .22 "kit guns", which hold 6. I like the Model 649--shrouded-hammer .38 in stainless steel. There's nothing sacred about 6 rounds; Sam Colt's first revolvers, the Paterson models, held 5 rounds. 5-round guns are structurally stronger anyway; the bolt notches fall between the chambers and not over them.
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