I have a Mexican Mauser that I had plans on a certain cartridge, but now I'm thinking of making a left turn on it...havent spent enough money on it yet.

This would be something I have not done before. How much diffrent is it to make a rebated cartridge such as the 284 Winchester feed compared to a standard cartridge. Is there anything to look out for that I might be missing. Went out to the shop and not a single 284 Win. in the place to look or play with, one reason I'm asking!