Hornady, winchester supreme for the good stuff. I don't think there's really any 300 win mag ammo that sucks!
for factory stuff at paper federal gold medal match 190 grain 42 a box in bulk (ten boxes) 50 a box for less. for hunting i like federal nosler partition in grain of choice for factory stuff about the same price as the other. black hills if you can find it in 190 grain is great paper stuff as well and cheaper.
you might give profire arms a call sight sponser on here. he will make up what ever load you want and will charge much less then the factory stuff. i like to shoot the same stuff for paper and hunting since i don't shoot for competitions. i preffer a 200 grain gameking bullet for the best of both worlds, but your rifle may disagree.
Just picked up a .300win mag, What are some of the ammo choices you guys prefer for target or range shooting?
I've bought a load of PRVI PARTIZAN 300 WIN. MAG. ammo, but I have shot any yet, so I don't know how it groups