I ran into a bit of a snag while installing the timney. The part about 'with a hard flat stone, brake the edge of the sear'. I'm not sure exactly what they mean. Do they mean file, shave, grind or polish? and if so, how much? The picture in the instructions was very vague. With only a gentle polish on the edge of the sear, I installed the trigger but it wasn't catching the sear. Anyone else encounter this on their M77???