I have been talking to Sierra, Hornady, Nosler, and Speer for more than 20 years. All of them say the the same thing. Elk hunting bullets in 300 mags should be 180 or 200 gr. because these bullets are built for 3000 fps. or more. Plus the jackets is made for elk CXP3 class game. Chuck Hawks has a bullet page that is a good read and he is not trying to sell anything.
As for powder I have shoot thousnds of rounds and too many different ones to count from a 300 Win. Nine times out of ten I will come back to IMR. 4350, 4831, or 7828 will most likely do the job. If I had to pick just one it would be 4831.
I now hunt elk with a 300 WSM less recoil. The bullet is Hornady 190 btsp. with Imr 4350. Hope this helps.