To answer the question. YES lapua brass is great. Setting the feeding issue aside for a moment, going to the 6x47L is not going to improve accuracy. I had one and found the only powder that shot extremely well was VV N560. with the 105 berger.
I had it rechambered to 243 Ack this case shot well with several powders including the 4350s. The 6BR is a great case and works out to 1000mtrs on days when conditions are good (not much wind). THEN THERE IS THE DASHER, the case for BR shooters.
Enjoy