Have looked all over but can't find a case drawing of this cartridge except length of 2.714" from the Lapua site. Aside from the quality of brass, what advantages does this cartridge have over a 338 UM?
The base diameter is approx. .586 with the shoulder diameter .544. The distance from the base to the shoulder is 2.161 and to the bottom of the neck 2.397 with 20 degree shoulder. The case should hold a few more grains than the 338 RUM and be slightly more effecient being that it is shorter and fatter. The draw back is that you have to have a larger bolt face and possibly action to use it. If money is a factor I think the RUM would do just about anything the Lapua would do and you could use a factory Rem 700 action. I chose to go the Lapua route myself as I wanted the better brass, efficency and I already have a 300 RUM and wanted something different.
Hope this helps some.