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Old 11-09-2019, 02:54 PM
Unclenick Unclenick is offline
Join Date: Nov 2010
Posts: 1,100

Funny that they got that far off. I have, I think, three of these tools and all are off, but not by more than 0.002". So I just drop a GO gauge in and remember what it says and offset my readings by the opposited sign amount.

Incidentally, you want to calibrate with a good quality GO gauge. I've got one "armorer's set" of .308/7.62 gauges for which the PM and the case comparator adapter on my calipers both tell me the gauge labeled 1.638" is a thousandth shorter than the one labeled 1.637". A couple of others are the same length but are labeled 0.001" different. I have had good luck with Dave Manson's headspace gauges. I would expect Pacific Tool to be good and I'm sure there are others. My point is just to be aware of the inexpensive ones, as they may not be dead on.

Most .308 and 7.62 new cartridges I've measured ranged from the SAAMI minimum headspace -0.003 to right on at 0.000 (some foreign surplus), with the majority being -0.002". I think that's where the idea that sizing to set shoulder location back by -0.002" for adequate feeding and maximum case life came from.

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Last edited by Unclenick; 11-10-2019 at 09:56 AM.
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