I have a WWII Webley chambered for the .38S&W or as it was called by the British, the .38/200.
I use 3.0 grains of Unique and a variety of bullets. The loads are mild and they work more or less well, depending on the bullet.
The real issue with handloading the .38 S&W is bullet choice. The proper bullets are .360-.361 diameter. I cast my own - from the Lyman 358430 mold which drops a 195 grain bullet at .360 using WW alloy. That allows me to duplicate the British service load. The three grain Unique load, by modern standards, is mild.
I also cast 140 grain LSWCs from a mold by CBE. Those bullets are also .360. I up the load to 3.5 grains, though the 3.0 grain loads works fine.
Many shooters who load for this cartridge use lead bullets meant for the .38Spl./.357 Mag cartridge. Some of those bullets work quite well, though they are undersized. I had success with 158 gr. LSWCs that were swaged - Hornady, IIRC. 148 grain Lead HBWC, seated halfway in are worth a try with mild loads of Unique or Bullseye.
Pete