Jump to 1:24 if you just want to see it in action. This pretty much makes it the best weapon for the last part of the Raid, the DPS is incredible and never stops. I have a video of me using it in the raid, it's the checkpoint before Oryx so don't watch if you don't want spoilers. I am speaking Portuguese btw because I exported this from the stream to youtube. Other thing that i tested is that if you are using Blessing of Light the last bullet takes life from your overshield, so just get inside and out of the shield and abuse that last bullet.
Its last bullet is infinate anyway with double damage, but at a cost of a portion of your health. 3 rapid kills will give you a portion of your health back