Maybe. But you will need to do further research to try to determine if this book was ever offered in a hardback version.

You have to consider the possibility that the book was rebound with a hard cover at some point. Bookbinding used to be a thing. It is still done, but the craft isn't as common as it once was. A good bookbinder or rare book expert might be able to determine if your Mauser book was rebound.

A true sign of mental illness is any gun owner who would vote for an Anti-Gunner like Joe Biden.