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Rifles, Reloading, Optics, Equipment
AR15/10 Rifles
go-no go-field gauge??
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<blockquote data-quote="msalm" data-source="post: 821752" data-attributes="member: 8863"><p>The math behind the depth reading is that headspace on a standard AR tenon is typically .750". I measure the bolt and barrel extension and chamber to that spec when I make AR barrels. Measurements vary from .750 to .752 on average with .750" being the norm. An easy way to measure headspace while chambering is to thread the extension on the tenon and measure from the back of it to the headspace gage. Most every barrel extension I've measured comes in at 1.121" with the exception of BAT extensions. They will measure 1.122". Take that measurement and subtract the .750-.752" and you will come up with an average difference of .370". This is the distance from the rear of the barrel extension to the back of the headspace gage for a zero headspace. You can add up to .004" from that and still be within spec, any more and you have excessive headspace. If doing this with brand new brass, you will have a slightly greater measurement depending on how undersized the new brass is.</p></blockquote><p></p>
[QUOTE="msalm, post: 821752, member: 8863"] The math behind the depth reading is that headspace on a standard AR tenon is typically .750". I measure the bolt and barrel extension and chamber to that spec when I make AR barrels. Measurements vary from .750 to .752 on average with .750" being the norm. An easy way to measure headspace while chambering is to thread the extension on the tenon and measure from the back of it to the headspace gage. Most every barrel extension I've measured comes in at 1.121" with the exception of BAT extensions. They will measure 1.122". Take that measurement and subtract the .750-.752" and you will come up with an average difference of .370". This is the distance from the rear of the barrel extension to the back of the headspace gage for a zero headspace. You can add up to .004" from that and still be within spec, any more and you have excessive headspace. If doing this with brand new brass, you will have a slightly greater measurement depending on how undersized the new brass is. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
AR15/10 Rifles
go-no go-field gauge??
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