Hk SFP9 Thin Braided Cable Inside?

[Shooter81]

While taking down my SFP9 I noticed a thin steel braided cable that at one end is attached to the inside of the magwell, and the other end is attached permanently attached to the trigger bar. I have no idea why this is? I tried googling it and come up with nothing. Does anyone else out that that has Hk SFP9 know what this is all about? (Actual picture below)

 

[danlm]

The trigger rebound spring keeps upward pressure on the trigger bar so the gun will function . It keeps the trigger bar up so it trips the catch release and the safety lever and also resets the trigger . .

 

[plinker 777]

 

[Import]

Yep....nailed it...I guess it is an unusual spring....