5th, Acurracy is going to depend on the rifle itself not the caliber as Roy stated. With that said, I don't think the improved has enough advantage over the standard to warrant the extra work involved. I would go with the standard Lapua or call Shawn Carlock and build yourself a 338 Edge. Better ballistics than the Lapua and the only downside was remington Brass. Although, you can now get Nosler brass (I think?) as an option to remington brass. Unlike the Lapua improved, there is no fire forming with the edge, you can form cases on your press.
The Lapua is a great round, Edge is a better round.....AND I SHOOT A LAPUA!
If I did it again, it would be an edge.
Member 7MM STW Club