If you want the Lapua you will have to go custom. I thought about this and beat that discission to death. In the end I had "TRGRMAN" Joe Starnes of "Long Shot Percision" Conrad MT. build mine. I would not change a thing. Joe steered me right and was vary fair on price. I drove up to get it, TRGRMAN and Smokin99 took me out to the range. First day I was banging steel at 1000, 1100, 1250... and even rang the 36" gong at 2100 yards.
I have nothing against the 338-378 but I will tell you this. You will love the Lapua and the Lapua Brass.