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Rifles, Reloading, Optics, Equipment
Reloading
Bullet touching lands reloading question
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<blockquote data-quote="bigedp51" data-source="post: 1446070" data-attributes="member: 28965"><p>I have Lake City 5.56 M193 ammunition that is .003 shorter than my GO gauge.</p><p>SAAMI minimum rifle headspace 1.4636</p><p>SAAMI max & min case shoulder location 1.4666 to 1.4595 or .007 allowable manufacturing tolerances. Meaning a new case could be .003 longer than the GO gauge or .004 shorter than the GO gauge and still be within manufacturing limits.</p><p></p><p>And do not forget SAAMI min and max headspace on the average chamber is .010. The GO and NO-GO gauges have .003 between them and are for setting up a new rifle or barrel. And the Field gauge gives you .006 allowable wear or lug setback from the NO-GO gauge.</p><p></p><p>On a British .303 Enfield rifle at max military headspace with a rim thickness of .058 you will have .016 head clearance. Your head clearance in the chamber is the same as the amount of shoulder bump from sizing.</p><p><img src="https://i.imgur.com/HK76WCp.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p><img src="https://i.imgur.com/3cOMj9s.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Pacific Tool and Gauge offers three lengths of headspace gauges per rifle caliber. In order from the shortest to longest, they are: GO, NO-GO, and FIELD:</p><p></p><ol> <li data-xf-list-type="ol"><strong>GO:</strong> Corresponds to the minimum chamber dimensions. If a rifle closes on a GO gauge, the chamber will accept ammunition that is made to SAAMI's maximum specifications. The GO gauge is essential for checking a newly-reamed chamber in order to ensure a tight, accurate and safe chamber that will accept SAAMI maximum ammo. Although the GO gauge is necessary for a gunsmith or armorer, it usually has fewer applications for the collector or surplus firearms purchaser.<br /> <br /> </li> <li data-xf-list-type="ol"><strong>NO-GO:</strong> Corresponds to the maximum headspace Forster recommends for gunsmiths chambering new, bolt action rifles. This is NOT a SAAMI-maximum measurement. If a rifle closes on a NO-GO gauge, it may still be within SAAMI specifications or it may have excessive headspace. To determine if there is excessive headspace, the chamber should then be checked with a FIELD gauge. The NO-GO gauge is a valuable tool for checking a newly-reamed chamber in order to ensure a tight and accurate chamber.<br /> <br /> </li> <li data-xf-list-type="ol"><strong>FIELD:</strong> Corresponds to the longest safe headspace. If a rifle closes on a FIELD gauge, its chamber is dangerously close to, or longer than, SAAMI's specified maximum chamber size. If chamber headspace is excessive, the gun should be taken out of service until it has been inspected and repaired by a competent gunsmith. FIELD gauges are slightly shorter than the SAAMI maximum in order to give a small safety margin.</li> </ol></blockquote><p></p>
[QUOTE="bigedp51, post: 1446070, member: 28965"] I have Lake City 5.56 M193 ammunition that is .003 shorter than my GO gauge. SAAMI minimum rifle headspace 1.4636 SAAMI max & min case shoulder location 1.4666 to 1.4595 or .007 allowable manufacturing tolerances. Meaning a new case could be .003 longer than the GO gauge or .004 shorter than the GO gauge and still be within manufacturing limits. And do not forget SAAMI min and max headspace on the average chamber is .010. The GO and NO-GO gauges have .003 between them and are for setting up a new rifle or barrel. And the Field gauge gives you .006 allowable wear or lug setback from the NO-GO gauge. On a British .303 Enfield rifle at max military headspace with a rim thickness of .058 you will have .016 head clearance. Your head clearance in the chamber is the same as the amount of shoulder bump from sizing. [IMG]https://i.imgur.com/HK76WCp.jpg[/IMG] [IMG]https://i.imgur.com/3cOMj9s.jpg[/IMG] Pacific Tool and Gauge offers three lengths of headspace gauges per rifle caliber. In order from the shortest to longest, they are: GO, NO-GO, and FIELD: [LIST=1] [*][B]GO:[/B] Corresponds to the minimum chamber dimensions. If a rifle closes on a GO gauge, the chamber will accept ammunition that is made to SAAMI’s maximum specifications. The GO gauge is essential for checking a newly-reamed chamber in order to ensure a tight, accurate and safe chamber that will accept SAAMI maximum ammo. Although the GO gauge is necessary for a gunsmith or armorer, it usually has fewer applications for the collector or surplus firearms purchaser. [*][B]NO-GO:[/B] Corresponds to the maximum headspace Forster recommends for gunsmiths chambering new, bolt action rifles. This is NOT a SAAMI-maximum measurement. If a rifle closes on a NO-GO gauge, it may still be within SAAMI specifications or it may have excessive headspace. To determine if there is excessive headspace, the chamber should then be checked with a FIELD gauge. The NO-GO gauge is a valuable tool for checking a newly-reamed chamber in order to ensure a tight and accurate chamber. [*][B]FIELD:[/B] Corresponds to the longest safe headspace. If a rifle closes on a FIELD gauge, its chamber is dangerously close to, or longer than, SAAMI’s specified maximum chamber size. If chamber headspace is excessive, the gun should be taken out of service until it has been inspected and repaired by a competent gunsmith. FIELD gauges are slightly shorter than the SAAMI maximum in order to give a small safety margin. [/LIST] [/QUOTE]
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