I looked for a drawing of the AI round and couldn't find one. But did see that the .243 is .4539 and the .243 AI is only .006 bigger at the shoulder at .4598, I don't think the 6.5x55 AI is .020 bigger. If you go too straight on the body you will have extraction problems. Does anyone have a drawing?
I'm using the first one, and recommend it due to reloading die availability. Search for 6.5x55 BJAI. Bob Jourdan of Precision Shooting magazine came up with it.
Well not to be a Yayy sayer however the 6,5x55 BJ or Ackleyfied is a great round with some very good performance. In a long/medium action it, set long it will really shine and if the twist will carry 160 grain bullet the case has capacity to make them zip a long in good speed.
I shoot with two guys running 6,5BJ and they are both really happy about there rifles. /Chris