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**Unclenick** · September 13, 2011, 02:34 PM

Kayser,

The answer is very simple. The Wilson gauge is a new ammunition case length gauge, not a chamber length gauge. If you look at the SAAMI drawings you will see the maximum length for new .308 ammunition cases is shorter than the maximum length for chambers.

The numbers are 1.634" max for a case and 1.638" max for a chamber (FIELD NO-GO). The chamber is supposed to be limited to 1.634", like the case, when it's new, but if your gun has enough rounds on it to set the lugs back a little, when you fire a cartridge with enough pressure to fully fireform the case to the chamber, it will be too long for the ammunition length gauge. But that doesn't mean your headspace is out of spec.

September 13, 2011, 02:34 PM	#22
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Kayser, The answer is very simple. The Wilson gauge is a new ammunition case length gauge, not a chamber length gauge. If you look at the SAAMI drawings you will see the maximum length for new .308 ammunition cases is shorter than the maximum length for chambers. The numbers are 1.634" max for a case and 1.638" max for a chamber (FIELD NO-GO). The chamber is supposed to be limited to 1.634", like the case, when it's new, but if your gun has enough rounds on it to set the lugs back a little, when you fire a cartridge with enough pressure to fully fireform the case to the chamber, it will be too long for the ammunition length gauge. But that doesn't mean your headspace is out of spec. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; September 16, 2011 at 08:54 AM. Reason: clarification