Well gentlemen , if you refer to the latest manual by Speer #14 , They have a load using blue dot powder listed . It lists a 210 gr GDHP bullet using 12-13 grs . It's interesting that Speer and Alliant are both owned by the same main company . I guess they don't talk to each other .
I have used the 13 gr load for many years with the 220 gr Keith swc and yes , it is my powder of choice for the 41 magnum in my S&W 57's and 58 . In fact it is one of two powders I prefer in the 45 Colt (S&W 25's )as well . The other is not unique .