Save open files with new encoding in Sublime Text 3

I would like to save multiple files in Sublime Text 3 with a new character encoding.

I have tried using the following key command to achieve this with no luck. Basically nothing happens when I press the key combination.

{
 "keys" : ["ctrl+alt+s"],
 "command" : "save_all", "args" :{"encoding" : "Western (Windows 1252)"}
} 

If I check the key binding in the console with sublime.log_commands(True) I can see that the key binding is working because it returns command: save_all {"encoding": "Western (Windows 1252)"} But Sublime Text is still not saving the file as Western (Windows 1252). If I reopen the file it says UTF-8.

Is this at all possible or is there perhaps something wrong with the key binding I am using?