I haven't been keeping up on new reloading stuff lately but just got a new Hodgdon manual and they talk about a new powder(to me) Supreme 780 which they claim is used in Winchester Factory loads for the 300 Win mag.It's a round powder so metering would be easy-- in their data they use a large rifle primer( Winch LR)and not a mag primer??? I have been using R19(72 gr) with 180 Nosler partitions and CCI #250 mag primers in my 300 but was thinking about working up a new load(Moose & Elk) using a new bullet--will try-- Sierra 180 Game King- 180 Fail Safe-180 Corelokt--Has anyone used this powder for their 300WM? if so How do you like it?? What primer and bullet are you using? any other info appreciated.