How to 'grab' a single bone.

I have a rope made of bones and want the player to be able to grab one of the bones and so when they move they drag the rope with them. This must also work with one end of the rope being constrained to a static location. My current attempt was to have a constraint on my player and when I run my function I’d use set constrained components to constrain the rope bone to my (for testing) gun bone on the default FPS character. This however makes the rope freak out and the bone I select stretch all the way to (0,0,0).