Board Thread:Out-of-Topic Threads/@comment-13892511-20140727084219/@comment-10412586-20140729105111

Go to "Settings" in your iDevice and choose "Gamecenter". From there you can change your Gamecenter username to the name you want in Six Guns. Then, go back to Six Guns and you will see that it is using your Gamecenter username instead of your Glive username.