Maybe my memory is shit. But what is direct fire on ISG and Pack Howie?
As insaneHoshi said it could fire low arc if there was a possibility. Which is better acc and much shorter time to target. And that is the hell of a difference. It's performance was completely different in direct and indirect modes. This was good for skilled players becouse unit performance depended a lot on positioning - just like mg or pak. On the other hand the performance was very inconsistent between maps and skill levels and that is probably why it has been changed.