When you are fighting a machine and you shoot off one of its components, I think you should be able to run up and loot it. So if you shoot the weapon off of a Runner, you can get the ammo from it, or get a Hunter’s Tick Pods before it is destroyed to use on it if you have that skill.
and if we can borrow ideas from other games, some machines could have a special weapon that you can shoot off and use. but the ammo on it is limited and you can’t keep it. like Horizon Zero Dawn.