hmm... i've got a 700 and i'm not sure whether the file system is the same as on the 505, but logically that should work... i do know there are a few differences with the user interface. are you looking (on the 505) in something called "all books" or "library" or something, after you eject it ? maybe either try it again or install calibre quickly (it's free and only takes a few seconds to install, and very easy to use) and use that to send them over.
or, somebody who has a 505 will surely come along soon and be able to tell you for sure.