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Rifles, Reloading, Optics, Equipment
Gunsmithing
How to accurately measure (not validate) headspace?
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<blockquote data-quote="Jeffpatton00" data-source="post: 1852732" data-attributes="member: 97649"><p>Thx, Mram. From this 6.5 PRC drawing, SAAMI says the headspace should be 1.6486" - 1.6586", or a full 100 thousandths of tolerance. Some responders have said it's not necessary to know headspace, just make sure it's within the safe range with go/no-go gauges, but it seems that view misses several points: 1) for precision, we try to load to a specific bullet jump that our rifle likes, 2) when we're sometimes testing the difference between a 0.010" - 0.020" jump, SAAMI's 100 thou tolerance is way too large for our purposes, we need to know the actual chamber dimension, and 3) for custom barrels, the SAAMI spec doesn't relate to custom chambers cut with custom reamers. These are the reasons that I think we need to know our chamber's dimensions, rather than just validating safety with go/no-go gauges. Otherwise, we're working blind instead of working from data, and in the quest for precision, data is king.</p></blockquote><p></p>
[QUOTE="Jeffpatton00, post: 1852732, member: 97649"] Thx, Mram. From this 6.5 PRC drawing, SAAMI says the headspace should be 1.6486" - 1.6586", or a full 100 thousandths of tolerance. Some responders have said it's not necessary to know headspace, just make sure it's within the safe range with go/no-go gauges, but it seems that view misses several points: 1) for precision, we try to load to a specific bullet jump that our rifle likes, 2) when we're sometimes testing the difference between a 0.010" - 0.020" jump, SAAMI's 100 thou tolerance is way too large for our purposes, we need to know the actual chamber dimension, and 3) for custom barrels, the SAAMI spec doesn't relate to custom chambers cut with custom reamers. These are the reasons that I think we need to know our chamber's dimensions, rather than just validating safety with go/no-go gauges. Otherwise, we're working blind instead of working from data, and in the quest for precision, data is king. [/QUOTE]
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How to accurately measure (not validate) headspace?
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