I use a
lot of Power Pistol, but I don't load 155's in .40 S&W. (Hmm, I don't load 155's in anything!
)
My most trusted source for published load data with Power Pistol to reference is Alliant's 2005 printed guide. This was the last one they made before ATK took over the load data and dumbed it down
horribly and wiped out numerous different bullet types and loads. The guides they print now mirror exactly the data offered on the web, which is cheap.
That guide shows 7.0gr as a
MAX load under a 155 grain Laser Cast lead slug, turning in 1,115 FPS at 32,300 PSI. 1.125" COAL minimum, and they used a Winchester WSP primer.
As a double-check, I also referenced my 2002 Alliant printed guide (which they also named "Volume 2") and it shows exactly the same data clear across the board.
Hope that helps. Start below that, please, and work toward it.