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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Crown, accuracy, and BC
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<blockquote data-quote="LouBoyd" data-source="post: 492996" data-attributes="member: 9253"><p>The shape and symmetry of the crown is only part of the story of how much a bullet is upset as it passes the crown. The shape and symmetry of the base of the bullet is at least as important, and the muzzle pressure has an important effect. If the muzzle pressure was zero as the bullet passes the crown neither crown symmetry or bullet base symmetry would have the same effect on accuracy relative to having a a few thousand psi of propellant gas blowing on the base of the unsupported bullet. Certainly there are many ways a crown can affect accuracy as can defects at other locations in the barrel. Barrels can damage or distort bullets before they reach the crown. Blowby can also take place in any enlarged portion of the barrel including at the crown. The properties of the bullet and it's ability to seal the bore over the length of the bore matters too. </p><p></p><p>Having a perfect crown does not insure accuracy, Bullet base symmetry is more important to group sizes than crown symmetry because the crown symmetry doesn't change angle from shot to shot. Accuracy and precision both come from repeatability.</p></blockquote><p></p>
[QUOTE="LouBoyd, post: 492996, member: 9253"] The shape and symmetry of the crown is only part of the story of how much a bullet is upset as it passes the crown. The shape and symmetry of the base of the bullet is at least as important, and the muzzle pressure has an important effect. If the muzzle pressure was zero as the bullet passes the crown neither crown symmetry or bullet base symmetry would have the same effect on accuracy relative to having a a few thousand psi of propellant gas blowing on the base of the unsupported bullet. Certainly there are many ways a crown can affect accuracy as can defects at other locations in the barrel. Barrels can damage or distort bullets before they reach the crown. Blowby can also take place in any enlarged portion of the barrel including at the crown. The properties of the bullet and it's ability to seal the bore over the length of the bore matters too. Having a perfect crown does not insure accuracy, Bullet base symmetry is more important to group sizes than crown symmetry because the crown symmetry doesn't change angle from shot to shot. Accuracy and precision both come from repeatability. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Crown, accuracy, and BC
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