I have a 6.5-06 ackley improved. It's not identical to a 280, but should be darn close to get you in the ball park on loads. I absolutely love the cartridge. If I ever build another I will likely build a 6.5x280 Ackley just to be able to buy factory brass and neck it down and cut out the fire forming step.
My gun really likes 140 Berger Elite hunters being pushed by Retumbo. Never got around to messing with the 156's because I would have ran into mag length issues. Plus the 140's shoot extremely well and perform excellent on game, so I've never had a reason to try anything else. My gun pushes the 140s at about 3,075 fps.
I don't remember my exact charge off the top of my head but I can look it up when I get home and PM it to you.