IIRC, bear in mind that some of this is coming from the deep dark recesses of memory,

The head diameter of a .50 BMG cartridge is around the ballpark with the 700 Nitro.

The .50 BMG cartridge development was commenced using cartridges based on the 16Ga.

In theory therefore, you could go to 700 Nitro.

I think.

If that checks out, fill your boots. (You probably will at some point in the process anyway).