I've heard mixed results from people using different forms of brass in their .43 Mausers. I hear Bertram is prone to splitting and the rim thickness can be way off sometimes. Some say reformed .348 works well. Some say it's dangerous. Some are saying to use reformed 45-70 or 45-90 shells. I see BuffaloArms just raised their price of .43 mauser ammo to $71 per box. So there goes that plan.
I think I may get a box of loaded ammo from Gads and then save the brass to load myself.