In several of Raymond Chandler's early short stories, some of which I've lately been rereading, his detective hero favors a Luger, at least once specifically described as .30 caliber. It's been a looong time since I read the novels and don't recall what he carried in them. In at least one of the short stories ("Red Wind") as originally published the hero wasn't named Phillip Marlowe, but was changed in subsequent publications.