I've had issues with my Shadow, Shadow T, and Compact L and my Kadet II. Probably about 10% light strikes. I didn't want to alter these guns in any way, because I like them just the way they are. I bought a 75B stainless which had been converted to SAO by CZC. I changed to a 17 pound mainspring and it is 100% reliable with the Kadet II upper. Changing to the heavier mainspring did not alter the trigger pull appreciably.