I'm not sure anyone chambers a factory rifle for .338 RUM anymore. Might be one in a catalogue, but finding one over the counter, or online even seems unlikely to me. Used maybe.
.338 Lapua, or .340 Weatherby will perform very similarly, if new factory is what you wish.
I am amazed that Remington stop making the 700 XCR in 338 rem ultra mag but you may be able to find one on one of the mail order sites. (Like Budsgunshop or Gun broker). It is a great cartridge J E CUSTOM