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Message: <blockquote data-quote="ASP785" data-source="post: 2614417" data-attributes="member: 12170">Traditionally most people will screw the sizing die down until it touches the shell plate, then turn it maybe a 1/2 a turn or so and start sizing. The problem with this is that depending upon the chamber of your firearm, you may be bumping the shoulder back too much. There are two problems with this. 1. Excessive sizing could lead to case head separation after repeated firings as the case expands to the point of failure in the critical web area. 2. Your accuracy may suffer. The first problem is a little bit more serious than the second.The solution to this is pretty simple. You need something like the Hornady Headspace Gauge: <a href="http://www.hornady.com/store/Headspace-Gauge-Kits/" target="_blank">http://www.hornady.com/store/Headspace-Gauge-Kits/</a>After firing a cartridge in the firearm you are reloading for, measure the cartridge using the tool and then screw your die down to either neck size only, or bump the shoulder back .001" to .002" for a bolt action firearm. For a semi auto gun, its best to go at least .004" back from the fired dimension for reliability. The tool will allow you to measure the shoulder moving back as you ever so slightly adjust your sizing die. Following this method of sizing cases will lead to longer brass life and typically be more accurate. However, it requires a specific set of brass for each firearm you shoot.</blockquote>