Re: 6.5x47 Ackley?
I may be wildly off base here, but from what I've read, the 40* shoulder is actually less than optimal compared to the better 30-35* shoulder, which, is already on the x47L cases.
If you need more powder capacity you might try the 6.5 creedmore or a 260 Imp. instead. The accuracy of the Lapua case is already supposed to be very well refined.