Available Cartridges
The BFR comes in two basic models, one with a long cylinder for big rifle cartridges, and one with a more traditional revolver cylinder length (called "short" by Magnum Research). Note that some models that use identical bores such as the .45/70 and .450 Marlin can be made with two cylinders for the same gun.
Magnum Research makes these guns in custom calibers and discourages the use of most rimless cartridges in their revolvers due to mechanical issues. The BFR can be customized for the .50 Beowulf cartridge. These revolvers were originally made by DMAX in Springfield SD until Magnum Research bought them out.
Read more about this topic: Magnum Research BFR