For minor 40 clays is my go to powder
4gr with a 140gr bayou was my favorite but 3.5 under a 155gr works you need a fast powder to make 40 work at low velocities
With WST I could not get my pistols to run reliably until I was well over 1000fps, my 140gr clays load runs at 975fps in a 5" barrel and runs at 27,000 psi (I used to have access to a real pressure lab so that's not a guess)
you could also try VV310 but I've never used it, I'm too cheap to get hooked on VV powder