Okay, so I need my companion to carry some of my ammo along with a few weapons so I'm not over encumbered, however, when I let them hold my ammo and a weapon that uses that ammo, they immediately switch to the weapon and use it to fight anything they see, thus, wasting my ammo. Is there any way that I can get them to hold my ammo and a corresponding weapon without them firing it off?

You can get either ED-E or Rex.

Nevermind, I found a work around.