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Rifles, Reloading, Optics, Equipment
Reloading
'Flattened' primer pictures?
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<blockquote data-quote="CatShooter" data-source="post: 126314" data-attributes="member: 7"><p><strong>Re: \'Flattened\' primer pictures?</strong></p><p></p><p>There are two kinds of "Head space"... the first is the minimum to maximum chamber dimensions, what is most often referred to when speaking of "HEAD SPACE" (in capitals) - which for, say the .223 is:</p><p></p><p>(ANSI/SAAMI Z229.4-1992)</p><p></p><p>To the 0.330" datum line, 1.4736" max and 1.4636" min. so the rifle chamber has 0.010" between minimum and maximum chambers from the factory.</p><p></p><p>Add another 0.005" for a field gauge and a rifle can be with in spec with a spread of 15 thou.</p><p></p><p>But to arrive at the real "working head space (little letters) add to this the case variations:</p><p></p><p>Cartridges have their own set of min/max dimensions...</p><p></p><p>... and here the .223 case (to the 0.330" datum line) would be 1.4666" max and 1.4596 min.</p><p></p><p>So the best combination would always be the minimum chamber and maximum case, which would be:</p><p>Chamber = 1.4636"</p><p>Case = 1.4666"</p><p>Which would be a case that was 0.003 over sized, giving you a crush fit.</p><p></p><p>But the opposite is also possible. A maximum chamber with a minimum case.</p><p></p><p>Chamber = 1.4736"</p><p>Case = 1.4596"</p><p></p><p>Or 14thou of working head space...</p><p></p><p>But there is a third variable.</p><p></p><p>I'm sure that you are aware that SAAMI specification are not mandated measurements. The set of books from SAAMI state "Voluntary Industry Performance Standards", which is a polite way of saying, "Please guys, try to stay inside these limits".</p><p></p><p>Most good custom gun builders do stay inside these limits, but in large factories (especially in the US), the adherence to these recommendations are loose and will easily add another 5 thou under production pressures.</p><p></p><p>To that, add the wear of the locking surfaces as the tool marks are rubbed off in the first weeks of shooting, and you have an easily achievable worst case of 25 thou of working head space.</p></blockquote><p></p>
[QUOTE="CatShooter, post: 126314, member: 7"] [b]Re: \'Flattened\' primer pictures?[/b] There are two kinds of "Head space"... the first is the minimum to maximum chamber dimensions, what is most often referred to when speaking of "HEAD SPACE" (in capitals) - which for, say the .223 is: (ANSI/SAAMI Z229.4-1992) To the 0.330" datum line, 1.4736" max and 1.4636" min. so the rifle chamber has 0.010" between minimum and maximum chambers from the factory. Add another 0.005" for a field gauge and a rifle can be with in spec with a spread of 15 thou. But to arrive at the real "working head space (little letters) add to this the case variations: Cartridges have their own set of min/max dimensions... ... and here the .223 case (to the 0.330" datum line) would be 1.4666" max and 1.4596 min. So the best combination would always be the minimum chamber and maximum case, which would be: Chamber = 1.4636" Case = 1.4666" Which would be a case that was 0.003 over sized, giving you a crush fit. But the opposite is also possible. A maximum chamber with a minimum case. Chamber = 1.4736" Case = 1.4596" Or 14thou of working head space... But there is a third variable. I'm sure that you are aware that SAAMI specification are not mandated measurements. The set of books from SAAMI state "Voluntary Industry Performance Standards", which is a polite way of saying, "Please guys, try to stay inside these limits". Most good custom gun builders do stay inside these limits, but in large factories (especially in the US), the adherence to these recommendations are loose and will easily add another 5 thou under production pressures. To that, add the wear of the locking surfaces as the tool marks are rubbed off in the first weeks of shooting, and you have an easily achievable worst case of 25 thou of working head space. [/QUOTE]
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'Flattened' primer pictures?
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