I read conjecture, but not confirmation, that basing on the .284 case would be against the rules. Given the range I'd expect that getting a heavy, high BC bullet going as fast as possible (& accurate obviously) is going to be crucial. Assuming unconfirmed, I still think that a .260 AI based wildcat, but using the .284 case for just a little more powder capacity, could be a contender. Make it the same OAL case length, and the same neck length, shoulder angle, and body taper as the .260 AI, just do it with the .284 case as the starting point.
