This past summer we had a crono stage set up at one of our local USPSA matches. I shoot 5" 1911 Kimbers, using 4.8gr of WST or 5.6gr of W231 with 200gr SWC.
5.4 gr W231 with 200gr Precision SWC averaged 768.9fps, or 153.78PF
4.8 gr WST with 200gr Precsion SWC averaged 830.5fps or 166.1PF
WST is inversely affected by temps, hotter the temps, the slower the PF.
Agree, you need a chrono to know for sure.