So far as black powder with the 280 gr. bullets is concerned, you just need to fill the case to the point where you compress the powder about 1/16 inch. With smokeless, you'd probably need to reduce the charge by about 12.5 percent to compensate for the heavier bullet. One thing you may encounter would be whether the rate of twist is fast enough to stabilize the heavier bullet. I've seen .40 caliber M1886's with a bunch of different twists. Seems like they couldn't make up their mind. You could measure the twist and run a bunch of calculations, but probably the best way is just to try them and see,