Professionals I've spoken with have said to replace factory .380 springs for proper 9x18 ones -- understandably I'd say. Obviously Wolff recognizes something there too which explains why they sell asst'd-weight Mak springs. In my opinion the Wolff 19 lb. spring could be OK with at least a .380+P cartridge (like Corbon's) but I personally wouldn't rely on it with run-of-the-mill factory loads. In fact, I'd use them with the 17 lb. option.