I don't use an expensive chronograph, and I don't routinely shoot through or over one unless I am diagnosing a problem or exploring new ground. Over the years, I have found SOME correlation between low SDs and accurate downrange performance, but the relationship is more like handmaid and queen than a royal marriage. Most of my moulds producing gas check shanks show a tight fit onto their respective checks (usually Hornady, a few newer Lyman, and the 6mm Gator). With a few designs, I am required to "spread" the check's opening a bit to ensure square fit, and have employed various punches or round objects to accomplish this. A little tap goes a long way here. Summed up, I have yet to blast a chronograph with a gas check flying off a bullet base. I am firmly knocking on my wooden puter desk as I type this.