Thread: Headspacing
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Unread 06-21-2018, 08:33 PM   #9
Mark1
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GT,
I have encountered the same or similar problems many times in the past. The issue is with some particular calibres or types of cartridge case and is due to the very large chamber dimension tolerances of the SAAMI specification. The solution is to use the much closer CIP (European proof and ammunition standards organisation) specification headspace gauges for all chamber work.
For example, the SAAMI spec. headspace tolerance range (Go-NoGo) for the 9mm Luger is .022" whereas the CIP range is .012". The same applies to the 45acp cartridge, SAAMI .022", CIP .012". For most rimless rifle cartridges, SAAMI headspace gauges will give a range of .010", the CIP gauges are .004".
I have no idea why there is such a large variation between the 2 standards, but for me a lot of the problem guns disappeared when I began using the CIP gauges. The best source of CIP gauges I have found is Pacific Tool & Gauge there in the United States.
Mark
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