Franchi: I have never installed one of these safeties that it did not require grinding to a "degree" on the safety to get it to smoothly go on and off. It is better to let this job be done by a gunsmith until you are familiar with the principals of the operation of the camming surfaces and their interaction with one another. Grind wrong and you can throw the safety away. The adjustment screw and spring are used after the correct grinding, to adjust the tension on the lever. HTH Good Luck Jerry