A number of people have shot a 6.5x55 Ackley, which would be the same except for the shoulder angle. Steve Shelp, for one, whom you met at Rachel's Glen. He did pretty well with it. As I remember, he tried the Lapua case, the Norma case, and the RWS case. At least one of them had a slightly greater capacity than the 6.5/284, but in any event, you'd be right around that capacity. I'm not sure how much you'd lose by having a 30-degree shoulder, but it wouldn't be all that much. Not sure if that's a plus or minus for your intended purpose.
Other people we know who have used the 6.5x55 Ackley are Dave Tooley and Joel Pendergraft, but I don't think either of them read this forum much anymore. Steve checks in from time to time, I can send him an email if you'd like.