gs50401: Since you do not own any 38 Special chambered revolvers but only use loaded 38 Specials in your 357 magnums, then you may wish to think about something Skeeter Skelton wrote about years ago.
If you are not familiar with the name, he is one of the 'known' gunwriters of yor (back when). He used 38 special cases in his 357 magnums when magnum brass and magnum ammo was hard to come by (50's and 60's). Skelton would take a 38 special case and with whatever bullet weight he used he would split the difference between the max 38 special loading and the max 357 mag loading for that bullet and that is what he would charge his cases with. The loads were higher pressured but accurate and easy on the gun.
If I owned just 357 magnum revolvers I would continue to follow the same practice but it is too easy to confuse the loads and hurt a good 38 special in the process. I followed his practice for a long time and used that type of load when I used a friend's round butt Model 19 snubbie to shoot metallic silhouette. At that time I loaded 158/160 gn cast swc slugs. Pressure levels were about the same as with the 357 mag and I could easily 'dong the gong' at 100 m with that snubbie. Later I went to a heavier 200 gn slug, they actually shot more easily and were very accurate, but I would have to wait for the darn gong to stop swinging so wildly after the first hit before I could take the second shot. With the 158 gn slugs the gong would swing but not as wildly and you could time your shots to hit it on the back swing - it was a hoot.
The Lyman Manual should have load data for the 195/200 gn slug, and you should be able to find similar information in Winchester's loading data. HTH. Mikey.