I wouldn't even bother myself. Just use the mid-range 38 special recipe as is. The load will be a few fps slower than the same load in a 38 special case, but so what?

It isn't like low-end 38 specials are so slow and under powered that they are going to stick in the barrel or anything.

Think about it, the 38 long Colt using the same bullet is loaded to lower pressures and velocities than the 38 special and they still make it out the end of the barrel, right?

A few fps due to the 10% larger case volume just isn't going to make that big of a difference. Worst case scenario if they aren't fast enough for you, use the top end of the 38 special charge weight. A max 38 special load isn't going to be all that hot in a 357 case.

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