Yup, it was officially the "IBM 3340 Direct Access Storage Facility", but it was designed to have two 30-meg disk packs, so internally everyone called it the "30 30", and owing to the rifle, the project became codenamed Winchester. Strictly unofficial, but ubiquitous in certain circles.
The product actually shipped with either 35 or 70 meg disks, so it was an immediate misnomer, but the name stuck anyway. You'll find references to it in old mainframe texts.
