I'm not a vastly experienced reloader and I haven't been reloading .40 very long but I do use Power Pistol and understand that it's one of the very strongest commercial powders available.
I found that my 6.4gr. loads of PP packed a considerably bigger punch than the Federal white box XM40HC's that I bought so I decided to tone it down considerably to the 5.6gr. range.
Especially for target range fare, I feel 6.4gr. of PP kinda puts unnecessary strain on a gun... (but I'm no expert).
What did Mrs. Bullet say to Mr. Bullet? ... "We're having a BeeBee!"...
IF THE SHOE FITS, WEAR IT!... IF THE GUN FITS, SHOOT IT!