I am a fan of Alliant powders. Their website has some good loads for your rifle. I am a real fan of RE33 for the big rifles. I have worked up some great loads with it for a 7 mag, too.
A couple buddies use Accubonds in their 300 Remington Ultra mags, I use Accubonds in my son's 300 WSM, and Accubonds in my 30-06. They are a fantastic bullet. It is hard to go wrong with either a Nosler Partition or E-tip as well! Best of luck.
I've had good luck with my 300 Weatherby with the 180 grain partition and reloader 22. I've used the partitions in my 300 H&H, 338 Win Mag and have had no failures to perform in accuracy and terminal performance on Deer, Elk & Moose.
Dan
I'm glad to see this post, the reason being is that a friend of mine has a Remington 700 in 300WBY, that when he purchased it had only 20 rounds through it,and then became a safe queen, for 5 years that my friend has owned it,it has been a safe queen also,up until a few weeks ago. The only work done to it was the barrel was floated. I've worked with him to get the rifle to shoot well, but have had no luck, he doesn't believe in reloading, but after a couple of hundred dollars spent on ammunition, he's looking at reloading as new option. Thank you.