Wolff makes a recoil spring calibration kit with a 7 , 8 (factory ) , 9 lb springs . Sometimes if spring is too light for the load , the gun unlocks too soon & you'll see vertical stringing . Extractors are available you have to beat the bushes though . If gun is new to you I'd change all the springs including the mags too . I'd also run the heaviest recoil spring that allows gun to function & slide to lock open on an empty mag .