This “How-To” video shows how to remove & replace the trigger group. Be sure to put your safety on so you don’t accidentally let the hammer drop.
It is NOT necessary to remove barrel or forend. Gun should be cocked, bolt closed, and safety on then proceed watching the video for further instructions.
The spring can be removed easily from a cocked hammer trigger group by grasping the spring between your thumb & fore finger. Replace with new spring by reversing the procedure.