Automount afp Volume with AppleScript

I know this is similar to other open questions about mounting network drives, but this one is slightly different.

I have an AppleScript that runs at startup that looks like this:

tell Application "Finder"
  mount volume "afp://192.168.1.105/file_server/user_name
end tell

Where user_name is specific to the sub folder under file_server. On one of my Macs, this works and mounts the sub-folder at user-name. On a different mac, it only mounts the file_server folder. The one that doesn't mount the full path is OSX 10.9.5. The one that works properly is OSX 10.10.1. Makes me think it's an OSX version difference.