If you mean the "280 Remington Ackley Improved", here is some data from the Nosler #5 manual:
140 grain Ballistic Tip or Partition:
IMR 4350 53.5 to 57.5 grains. 2911 to 3134 fps. Fed 210 primer. Remington case. No OAL given.
Reloder 19. 56 to 60 grains. 2904 to 3146fps.
IMR 4831 54.5 to 58.5 grains. 2920 to 3164fps. Most accurate powder.
160 grains.
IMR 4350. 51.0 to 55 grains. 2722 to 2901 fps.
Hodgdon 4831sc 52 to 56 grains. 2715 to 2855.
This manual has a lot of load data for this cartridge, so you probably want to get a copy.