The Starline brass is not 9x23 brass, it's 9mm supercomp. Most of the dimensions are a little different,including the thickness of the web. I've noticed the Starline brass cracks long before the winchester brass. If you had your chamber reamed for the 9mm supercomp dimensions it would probably last a little longer. I now buy only winchester brass. It cost a little more, but I'm worth it. So are my guns.