Hello all, If my guitar is setup in standard, is it ok for me to tune it a half step down? Or will it mess up the action and whatnot?

of course you can. just make sure you tune down all the strings a half step. if you want to go back to standard, just tune them back up a half step
The concern with this is that your intonation may go a bit off and notes higher up on the neck won't play in tune. You can remedy this by tuning all the strings correctly, then using an electronic tuner on the twelfth fret using the screws on the bridge (depending on what kind of bridge your guitar has) to set the notes correctly.

The action should stay more or less the same tuned down a half step, but the strings will feel a bit looser and the sound will be darker (which some people like).
Gibson ES-137C
Parker P8EN
AC Custom Special P Bass
If you have a floating bridge, then you might have a little trouble, otherwise. Should be fine.

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