If you want companions to use a weapon that is not their own, you have to supply them with ammo.
Same as Fo3. My blue ray should have burned clean through the disc for the amount of time it was in my ps3. Im assuming this is a bug cuz boone wont use a gun now. I select it frome the menu, say a 10mm smg with 400 rounds. Bam, he goes to melee every damn time. sorry op!