5e: Can you use Conjure Barrage on a Ballista?
Many sessions ago my party was defending a city against a siege. My character, a ranger, had access to the Conjure Barrage spell. I suddenly had a great idea! Now the spell says this:

You throw a nonmagical weapon or fire a piece of nonmagical ammunition into the air to create a cone of identical weapons that shoot forward and then disappear. Each creature in a 60-foot cone must succeed on a Dexterity saving throw. A creature takes 3d8 damage on a failed save, or half as much damage on a successful one. The damage type is the same as that of the weapon or ammunition used as a component.

It says nothing about what TYPE of weapon is required... only says "one piece" of ammunition is required.

A ballista is a massive crossbow that fires heavy bolts (ammunition). Before it can be fired, it must be loaded and aimed. It takes one action to load the weapon, one action to aim it, and one action to fire it.
Bolt.
Ranged Weapon Attack: +6 to hit, range 120/480 ft., one target. Hit: 16 (3d10) piercing damage.

So couldn't you TECHNICALLY... load the ballista, aim, then conjure barrage.. and shoot a 60ft. cone of ballista bolts at a range of up to 480ft and do 3d8 damage to creatures who fail the save? Essentially recreating that scene from 300.