If you don't mind having your 280 loads having a 30-06 headstamp...
When you get your 280 loading dies, get yourself some 30-06 brass, new or used, and just run them into your 280 die.
As the 280 body is 0.050" longer than the '06 body and the 280 neck is 0.025" smaller than the '06 neck what you'll get is a "false" shoulder in the neck area for your loaded cartridge to headspace on.
At this point you can either load a reduced charge, say something in the neibourhood of duplicating a 7x57 load, or you can fireform the brass in your chamber and load full pressure loads.
Your 280 brass formed from '06 brass will be 0.050" shorter than factory spec., but that won't cause any problems unless you're looking for target accuracy. And the money you save on brass could always be used to buy better bullets. After all, it's really the bullet that does all the work not the "fuel-tank" used to launch it.
As always, if you use military surplus brass, reduce your loads accordingly due to the thicker brass used leading to reduced case capacity.
And if you also own an '06 don't worry about loading the wrong ammuntion in the wrong chamber.
Because of the 0.050" longer cartridge body of the 280 over the '06, if you mistakingly load the 280 into the '06 chamber you won't be able to close the breach of the '06.
And because of the larger neck size of the '06 you won't be able to load it into the 280 chamber.
If you have any other questions about doing this or it's safety I suggest that you post your questions on the gunsmith board as I am not a gunsmith nor pretend to be.
Hope this helps...
Lowtech...
