The best thing to do (if you shoot factory ammo) is to buy rounds from all the various manufacturers, Remington, Hornady, Winchester, Federal, etc. Over a period of time, shoot them for accuracy at 100yds and find out which one wins. When you find what works best in your rifle, buy a case of it (or more) especially if you can get the same lot.
I have done this for a few rifles that I don't or don't want to reload for. One of them, a 1960's Remington 700 7mm mag., loves Winchester Ballistic Silvertips so I shoot those, they clover leaf at a 100 yards prone off a bag. I purchased all the boxes I could in the same lot and finally ran out a year or two ago. I was worried that the lot difference would change the poi with a new lot but it didn't. 10+ years later and the poi is the same, irregardless of the lot.
It is expensive to do (now days) but well worth it. I am now in the process of doing it with an LR-308 long-range setup.