Post-1957 Smith & Wesson Model 31 Regulation Police revolvers chambered for the .32 S&W Long and .32 Colt New Police are actually stout little revolvers and will perform happily with loads which you wouldn't dare use in an earlier .32 Hand Ejector.
I have one of these with a 4" barrel which I carry all the time as a kit gun, and find it much more effective than a .22 LR.
My favorite handloads use the Saeco #325 90-gr. Keith-style SWC bullet, cast of wheelweights, sized .313", tumbled in Lee Liquid Alox, in Remington cases with WSP primers:
Min. Start 1.8 grs. (factory equivalent 720 f.p.s.) Alliant Bullseye
Maximum 2.6 grs. (modern solid-frame only 850 f.p.s.) Alliant Bullseye
Also good is 3 grs. of W-W231 with the same bullet.
If you want an expanding bullet for varmint use which will shoot to point of aim with the iron sights, use the 85-gr. Hornady XTP JHP with either 3 grs. of Bullseye or 3.5 grs. of W-W231. Do not exceed.