The up hotkey on PS3 is taken up by something already, and I can't change it. I dont know what is in that slot, and I cant really figure out what the little pic is showing. It looks like two bullets with arrows in between but it doesnt seem like I'm switching ammo types or anything like that when I press it. Any one help?

Also wondering this. Perhaps it switches ammo types or something?

I have no idea to be honest (PS3 gamer too), I thought it was some error on my end, glad to know it's some item.

Yep, it switches ammo types.

If you have a weapon out and multiple types of ammo available for that weapon it will switch between them.

Switches through ammo types.

It is for what ever weapon you have out and using at the moment. If you have different types of ammo for it, then you switch between them. But you have to have the ammo on you to be able to do this.

Am I too late to say that it's for switching ammo types?

It switches out ammo types.
You have Surplus.
Armor Piercing.
Incendiary.
Hollow Point.

Gotta buy them at the stores though.