If you are going to the expense of building a double rifle and if you handload, you might want to consider the most potent 9.3- the 9.3X64. I've used it with great sucess; using reduced loads for deer and neck shots on buffalo (bison) and at full loads it is the equivalent of the 375 H&H.The other option- the 375 H&H is a very flexible cartridge,ammunition can be bought in about any sporting goods store, and new Merkel, Krieghoff or other brand double in 375 H&H will probably be cheaper then having a double built.Just some thoughts-