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Rifles, Reloading, Optics, Equipment
Gunsmithing
Neck clearence on a Match Reamer
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<blockquote data-quote="sable tireur" data-source="post: 1328062" data-attributes="member: 27307"><p>The term 'Match' in conjunction with reamer making has changed definitions over the years. I questioned Dave Kiff about his labeling some reamers as 'Match' and his response was, 'any reamers which had specifications outside of SAAMI/CIP spec were labeled 'Match" unless there was a specific name with known dimensions attached to a particular reamer.' The Diego XYZ Super Duper Atom Smasher.</p><p></p><p>None of the rifles I've built have used more than 0.004" for neck clearance including those used for Dangerous Game. </p><p></p><p></p><p></p><p>This is simply not true unless there are extenuating circumstances. Most of us have been using 0.002" clearance for the last 3 decades that I can think of and none of us have experienced 'excessive pressure' given <u>normal circumstances</u>. All that's required is enough diameter for the case neck to expand in order to release the bullet. On the other hand, everyone is entitled to an opinion about how they want to do their work. </p><p></p><p>Regards.</p><p></p><p>ADDED:</p><p></p><p>CIP, SAAMI and other specifications allow manufacturers to make cartridges and to cut rifle chambers that conform to rigid specifications. The specifications for chambers set a minimum size with an upwards tolerance. The specifications for cartridges set a maximum size with a downwards tolerance. This is to ensure that the smallest chamber for a given cartridge, will always accept the largest allowed cartridge. The manufacturers of reloading dies also follow these specifications.</p><p></p><p>When the smallest allowed cartridge is fired from the largest allowed chamber, accuracy will not be good. The critical dimensions for accuracy are the freebore and neck areas.</p><p></p><p>The maximum allowed difference will allow a clearance of 0.060 mm (2.4 mil)(0.0024") The closer to zero clearance one goes, the better the alignment will be and the easier accuracy will become.</p><p></p><p></p><p>When the cartridge is fired, any clearance between the cartridge neck and the wall of the chamber will become the clearance between the inside of the case neck and the bullet. The case expands away from the bullet until it contacts the chamber wall, before the bullet has moved much.</p><p></p><p>The more clearance there is between the case and the bullet, the more the long axis of the bullet can turn away from the centerline of the barrel. This causes the bullet to enter the rifling at different angles from shot to shot and results in different points of impact.</p></blockquote><p></p>
[QUOTE="sable tireur, post: 1328062, member: 27307"] The term 'Match' in conjunction with reamer making has changed definitions over the years. I questioned Dave Kiff about his labeling some reamers as 'Match' and his response was, 'any reamers which had specifications outside of SAAMI/CIP spec were labeled 'Match" unless there was a specific name with known dimensions attached to a particular reamer.' The Diego XYZ Super Duper Atom Smasher. None of the rifles I've built have used more than 0.004" for neck clearance including those used for Dangerous Game. This is simply not true unless there are extenuating circumstances. Most of us have been using 0.002" clearance for the last 3 decades that I can think of and none of us have experienced 'excessive pressure' given [U]normal circumstances[/U]. All that's required is enough diameter for the case neck to expand in order to release the bullet. On the other hand, everyone is entitled to an opinion about how they want to do their work. Regards. ADDED: CIP, SAAMI and other specifications allow manufacturers to make cartridges and to cut rifle chambers that conform to rigid specifications. The specifications for chambers set a minimum size with an upwards tolerance. The specifications for cartridges set a maximum size with a downwards tolerance. This is to ensure that the smallest chamber for a given cartridge, will always accept the largest allowed cartridge. The manufacturers of reloading dies also follow these specifications. When the smallest allowed cartridge is fired from the largest allowed chamber, accuracy will not be good. The critical dimensions for accuracy are the freebore and neck areas. The maximum allowed difference will allow a clearance of 0.060 mm (2.4 mil)(0.0024") The closer to zero clearance one goes, the better the alignment will be and the easier accuracy will become. When the cartridge is fired, any clearance between the cartridge neck and the wall of the chamber will become the clearance between the inside of the case neck and the bullet. The case expands away from the bullet until it contacts the chamber wall, before the bullet has moved much. The more clearance there is between the case and the bullet, the more the long axis of the bullet can turn away from the centerline of the barrel. This causes the bullet to enter the rifling at different angles from shot to shot and results in different points of impact. [/QUOTE]
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