Luna's Howl is a 180 RPM hand cannon, meaning its base damage would allow a 4-shot kill. However. the Magnificent Howl perk allows a 3-shot kill. If your first two shots are both crit hits, fired in quick succession, than the perk will activate and your 3rd shot will be strong enough to kill the target. Even a body shot against a max-resilience guardian will be enough to finish them off.

On paper, the perk should then deactivate, as you've just scored "a kill". But for some reason, it doesn't. It seems to me like there is a sort of "grace period", whereby if you score a kill immediately after the perk activates, it won't "count" and the perk will remain active. In practice, this is significant because it means I can kill an enemy guardian with 3 shots, then immediately turn to another target and kill them in 2 shots.

https://xboxdvr.com/gamer/nevindouglas/video/62725931

It's no secret or surprise that Luna's Howl can kill in 2 shots (I've been on the receiving end of it many times). But I'd always assumed that those were situations where my enemy had hit (but not killed) another guardian with 2 precision shots, activated the perk, then turned to me and blown me away. But the way the perk actually works is far more dangerous, because the person using Luna's Howl doesn't need to leave their first target alive in order to make use of the perk. This makes it an absolute monster when it comes to chewing through multiple targets. You can kill 2 guardians in roughly 1.65 seconds. O_o

https://xboxdvr.com/gamer/nevindouglas/video/62725948

What's that pulse rifle in the first clip?

Bygones (the Gambit pulse rifle). Mine has kill clip (which makes it a 2-burst kill while the perk is active), full auto, maxed-out Range masterwork and a Targeting mod. It’s a monster :)