I would think that without the barrel to enclose the gas pressure and direct the bullet in a single direction for a few critical microseconds, the bullets would just explode without becoming ballistic projectiles. But I don’t know, I’ve never set a bunch of them on fire and waited. It’s not that I’m not stupid enough, I just never got around to it.
Mythbusters did a segment where they put different ammo into a barrel and set them on fire. No projectiles, they just ignited like firecrackers....