Just bought a 1985 Marlin 40-65 rifle. I believe it to be rebarreled. The previous owner was left handed and I need to change the hammer extention to the other side. I figure it to be an allen screw inside the knurled knob. I broke a 1/16" wrench this morning after soaking it for several days / breakfree oil. What are my options? Am I correct in how this piece comes off?