I’m new to reloading and haven’t taken any classes yet but why don’t they make a 5.56 headspace case guage but do sell .223 gauges ?
The .223 Remington Headspace case gauge is suitable for 5.56x45mm since the external case dimensions are the same. It's the difference in chamber cutting and powder charges that make them different. To my knowledge, Accurate is the only powder manufacturer that actually lists separate load data for .223 Remington and 5.56 NATO (pages 28 - 32):
http://www.accuratepowder.com/wp-content/uploads/2010/09/WesternLoadGuide1-2016_Web-1.pdf
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