Downed Fire lets you shoot even when you're Incapacitated, but only with your backup weapon, and only after an initial delay. You will have almost no Health while Incapacitated, making it easy for enemies to finish you, so it's less likely that a Medic will be able to revive you.
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I'm surprised downed fire is rank 5, that means it will be a long time before we start seeing enemies shooting at you from their death bed :ahhh: