Currently using IMR 7828 in my 7mm/300wby but would like to try some different powders. My load of 74 grs pushing a Sierra 168 gr MK in WBY brass with a Fed 210M primer works very well. However, this charge does not fill the case and I would think a full case of another powder may be more efficient. All suggestions and comments will be appreciated.

I'd be thinking about Reloader 25 or maybe Retumbo from what I've heard of it, though I've not used the latter. RX25 is my powder of choice for the .300 Weatherby and I'd guess it would be superior to IMR7828 for you. FED 215 Primers BTW.