Just got my Jewel trigger for my FN SPR and opened it up to read the instructions. This is suppose to be a drop-in unit according to Sinclair Intl. personel. Now, this thing is talking about grinding on my trigger guard, filing this and that, and that ain't no drop in unit. Does anyone know whether all this is neccesary or not. If so, I'll just turn this thing around and do something different. I ain't grinding on my trigger guard. Any advice would be appreciated. Bill