Schuler developed the 11.2x72 (.440 bullet) in the early 1920’s, past that maybe the Brits, Germans and USA were too busy with 2 World Wars a Depression, and recovering from them between 1917 and 1950 to worry about a .450 bolt gun?
Then there was the .450 ban in India and the Sudan up to I think the late 1920’s and India was a much bigger market than Africa by all accounts.
- Mike