This is for my 7mm stw. I’m working up a load using the Sierra 165 Gamechanger. Powder is magnum and this was 77.7 grains with a coal of 3.625. Shot a five shot group and after the fourth shot I got this piece of brass. You can see the dent below the shoulder and the crack-which I would ordinarily call a headspace crack-I had this happen one other time, also only one of five shots and that was when I was testing the load at 3.615. I’ll run it by the gunsmith for his thoughts but any of you have ideas for me?