Be aware that you'll need a .338 Lapua action if you decide to go that route. They are heat-treated differently than standard large shank long actions to withstand the higher pressures of that cartridge. Most barrel manufacturers will not make Lapua prefits for this very reason.

The .300wm will certainly get you to 1,500 yards, but the heavier .338 caliber bullets are really going to outshine it for any type of shooting beyond 1k. If you're on a budget, I'd recommend doing exactly what Dennis said... The .338 Edge is certainly a viable option, and can be built on a standard large or small shank action - just be aware that reloading components (dies, brass, etc.) are relatively hard to come by and are expensive when you do.