Don`t know if it`s still in print, but if so, buy his book on Mauser Rifles. Everything you need to know.
I'm pretty sure I had that book once. I can't find it. Grrrr
Used copies of the book are readily available on the Internet--but naturally cost more than they did originally. With just a little Googling I found them for $70 up.
Another very useful reference is MAUSER MILITARY RIFLES OF THE WORLD, by Robert D.W. Ball. It can be found for around $50, but there's also a Kindle version.
Years ago Ludwig Olson phoned me,after reading one of my articles. (He went by "Lud.") We had a very interesting conversation. Unfortunately he passed away not long afterward.