I recently switched jugs and noticed a big drop in velocity. I've been using WST behind my 150gr Blue Bullets for a couple years now, so I had a lot of historical data from jug to jug. 3.6-3.8 always got 133-135 PF out of my g17/34's.
After the switch, I was barely making 126PF on my Caldwell chrono and steel poppers at a match where a problem. I turned it up to 11(4.2 grains) and I'm barely making 130 out of my 34. It's enough that I'm dropping WST after I run this jug out(no major matches soon).
It's also worth noting that Hodgdon/Winchester does not list WST as a 9mm powder anymore on their website's data page.
Since someone will ask, I'm moving to TitsGroup.