If memory serves the 30 cal luger round was thought to be a proven round for taking game. But it wasn't your average 30 cal round but one specifically made for the carbine. This was later phased out because people would use it in the regular lugers and damage their guns.
I could be wrong but that's how I remember it
I like the idea of a bottle neck round, you can get some interesting powder burning curves that just don't happen with straight wall rounds. The new powders on the market produce lower pressure curves and might prove handy in developing a hot new luger round.
Good Luck!
Please let us know all that you find out
Vern