Long action...
You can get away with a short action, but-
The reason for the 6x284 is long range, and long range means long bullets, and in a short action you will be seating them deep in the case. This takes up valuable powder space.
Built on a long action, you can use the magazine. You can load the long bullets out to touch the rifling, and still unload unfired rounds without removing the bolt.
I made the mistake of building a long case cartridge on a short action years ago, and if I don't fire the round, I have to remove the bolt to get the unfired round out of the action /ubbthreads/images/graemlins/frown.gif /ubbthreads/images/graemlins/frown.gif /ubbthreads/images/graemlins/frown.gif
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