My 20" FNAR Heavy likes 150 grainers a bit better than the heavier rounds. The Federal 150 grain soft points are affordable, pretty accurate and still punch hard. The UltraMax rounds shoot great in my M1A but the FNAR grouped worse with those. At the end of the day, you will see every rifle prefers different food.
I found out what mine liked by buying a box of each and making a good day at the range trying 5 or 10 of each. Like i said, mine liked the 150s. Hope that helps a bit.