IRL most ammo carriers won't be armed and if armed will be carrying different kind of ammo and even if they carried right ammo, they'd be frowned upon if they did take their cargo on their leisure barring extremely critical situation - the point of armament on armed ammo carriers is IRL to defend against say sudden ambush and gain time to drive away, not to stay and duke it out. And if ammo carrier reaches its destination with 10 attackers killed but without its load, I think the commander of its target unit won't be overly happy with the crew
