Recognize S&W had been boring 38 S&W barrels for almost 75 years with its unique barrel dimensions and as used in the 38/200 Victory models. S&Ws chambered in 38 S&W all have the original production tolerance groove diameter of .3595" -.3612" and Bore of .354" per Roy.

The new .38 spl arrived in 1899 with the first K frames in that caliber with its own unique bore dimensions.

So .357"-.358" bullets work quite well I'm told with no demonstrable accuracy difference using standard loaded .38 Spl ammo. With hotter loads the possibility exists that .357-.358 bullets may strip the rifling depending on the hardness.

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Jim
S&WCA #819