wld783,
Since the 300 Whisper is the kissing cousin to the 357 Mag I checked my Hodgdon reloading manual #27. They list a couple of different loads for various bullet weights. I think the closest one is there load for 170 gr Sierra HHC. Here are the data:
170 gr sie jhc
Titegroup
5.4........34700 cup.......6.0.......41800cup
You can go to the Hodgdon site and check for other loads here:
http://data.hodgdon.com/main_menu.asp
If you are going to try this powder in a 300 whisper AR15, I doubt that it will cycle the action because the powder is too fast.
Good Luck and let us know how it works
320pf