Hi @davisshaver
I believe that the publish action is run before the save action. ACF uses teh save action, so I don’t think any priority number will get your code to run after acf. Instead, you should use the save_post action.
Better than that, you should use the acf/save_post action.
You can read more about this here:
http://www.advancedcustomfields.com/resources/actions/acfsave_post/
Thanks
E