This afternoon I purchased a Ruger 77 Hawkeye in 280 Remington w/22" barrel.
1st 3 shots fired were Remington factory 150 core-loct psp and grouped 1.375" center to center.

I'm hoping to get some success and failure stories on the 280 with a 22" barrel.

Try 57.5 gr. of IMR 4831.... Mine is shot out of a Remington with 22" pipe. It probably won't matter but COL is 3.250, WLRM primer and RP brass at 2.530....this will shoot 1/4" and under in my CS

139/140-grainers and RL-19, IMR 4350 [56 grains +/-]

54 grs IMR 4350
56 Grs IMR 4831
140 grain Sierra SPBT
WLR PRIMER

Not bad for the first three shots. Your factory rifle is brand new, the barrel needs some time to 'break in' before it gives the best groups. Don't worry much about group sizes until you get at least 50+ rounds through it.



.

I've done some accuracy testing using 160 grain Hornady, Speer, Sierra, and Nosler bullets with RL19. I can't find one of them that doesn't shoot out of my Dad's Browing X-Bolt. What I can tell you for sure is that the Nosier Partition was head of the class (by the slimmest of margins mind you). Nosler #6 manual seemed to hit the nail on the head as far as powder weight charges were concerned with any of the aforementioned bullets.