Hi Adam,

For a one-off, scripts background will do it.

Standard disclaimer: The following code is untested, requires review and potential modifications.

(function () { 

       var rec = new GlideRecord('pm_project_task'); 

       rec.query(); 


       while (rec.next()) { 

             rec.short_description = rec.u_task_name;

             rec.setWorkflow(false); // do not trigger business rules/workflows

             rec.autoSysFields(false); // do not update system fields

             rec.update(); 

       } 

})();