The way I look at it is ask yourself how many deer, elk and bison have been killed with black powder loaded .45-70s in the last 130 yrs or so and they didn't have the great bullet selection we have today!! You can easily equal or exceed .45-70 trapdoor ballistics with a modern inline .45 cal, so I don't agree with the
need for a .50 cal which will work just fine, too. Get the one you have confidence in, you'll be happy you did!
I just happen to have a Black Diamond Super XR .45, been there with the .45 vs .50 debate!!
Tim