Here is the detailed list of changes and improvements included in the Game Server Update (R52 Server Update) on Sep 14. All changes apply to all platforms unless explicitly stated otherwise.

• Fix for a build issue resulting in a FrameHistoryTime of 0.125 in place of the intended 1.0. This will significantly improve on so called "dusting", particularly in fast vehicles.
• Fix for Hardcore preset switching to Custom/Unknown.

You can find the documentation for the R52 server version here:
http://eaassets-a.akamaihd.net/dice-games/BF4/ServerDocumentation/BF4_PC_Server_R52_166185_Docs_ServerAdministrator.zip