Good choice on the M18 Smith...it's one of my favorites as well.
I vary considerably, but this week I've been working with some target+ (850-900 fps) full wadcutter loads, here on the farm. Put up in .38 special brass, the velocity makes them a real carry option, and the short .38 case makes the ejection stroke more effective from my 3" bbl'd M60 Smith. The combination's fun, superbly accurate, and very economical with home cast bullets & Bullseye powder. The gun's good for tennis ball size offhand groups at 25 yds too!
Last week, BTW, it was a Smith M27 with a 5" bbl. Great gun, beautifully made, but just to heavy for me now in my dotage. Week prior, it was a M66 Smith, for those that care.
Best Regards, Rod