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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Explain How 7 PRC Has Tighter Tolerances VS 7 MM Rem Mag, without bashing any company
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<blockquote data-quote="WapitiBob" data-source="post: 2994195" data-attributes="member: 38015"><p>There is nothing wrong with the chamber, the virgin brass is short.</p><p></p><p>"Peterson makes the traditional SAAMI spec'd version that headspaces off the belt. But it also makes a version that headspaces off the shoulder. Peterson calls that version the 7Rem Mag "Long". <em>This listing is the LONG spec version."</em></p><p></p><p>Derek Peterson, president of Peterson Cartridge explains, "Traditional .300 Win Mag casings tend to show signs of case head separation after only 5 to 7 firings.</p><p></p><p>"Here's why. The SAAMI specs for any caliber, list a minimum and a maximum tolerance for each dimension on the casing and the rifle's chamber. With most calibers, the max dimension of the casing, for length-to-shoulder (L-T-S), has the shoulder of the casing right up against the chamber wall. With .300 Win Mag, unlike most other calibers, if your rifle's chamber is cut to the SAAMI minimum for L-T-S, and your casing is at the max length-to-shoulder dimension, the casing shoulder is still .0095" away from the chamber wall. With the same minimum rifle chamber, a casing at nominal L-T-S is .012" away from the chamber wall. In a worst-case scenario, if the casing was produced at the SAAMI minimum L-T-S, and the chamber was cut at the maximum L-T-S dimension, the casing shoulder could be up to .026" away from the chamber wall. That might not sound like a lot, but it is.</p><p></p><p>"That large gap is what causes the casing to stretch so much when it is fired. It's that stretching that causes premature case head separation."</p><p></p><p>Peterson continued, "With Peterson .300 Win Mag- Long casings, we make them with a longer L-T-S dimension. All the other dimensions are SAAMI spec. But the longer L-T-S prevents the casing from stretching excessively on the 1st firing. The casing has more support, which translates to less stretching, which translates to longer case life."</p></blockquote><p></p>
[QUOTE="WapitiBob, post: 2994195, member: 38015"] There is nothing wrong with the chamber, the virgin brass is short. "Peterson makes the traditional SAAMI spec'd version that headspaces off the belt. But it also makes a version that headspaces off the shoulder. Peterson calls that version the 7Rem Mag "Long". [I]This listing is the LONG spec version."[/I] Derek Peterson, president of Peterson Cartridge explains, "Traditional .300 Win Mag casings tend to show signs of case head separation after only 5 to 7 firings. "Here's why. The SAAMI specs for any caliber, list a minimum and a maximum tolerance for each dimension on the casing and the rifle's chamber. With most calibers, the max dimension of the casing, for length-to-shoulder (L-T-S), has the shoulder of the casing right up against the chamber wall. With .300 Win Mag, unlike most other calibers, if your rifle's chamber is cut to the SAAMI minimum for L-T-S, and your casing is at the max length-to-shoulder dimension, the casing shoulder is still .0095" away from the chamber wall. With the same minimum rifle chamber, a casing at nominal L-T-S is .012" away from the chamber wall. In a worst-case scenario, if the casing was produced at the SAAMI minimum L-T-S, and the chamber was cut at the maximum L-T-S dimension, the casing shoulder could be up to .026" away from the chamber wall. That might not sound like a lot, but it is. "That large gap is what causes the casing to stretch so much when it is fired. It's that stretching that causes premature case head separation." Peterson continued, "With Peterson .300 Win Mag- Long casings, we make them with a longer L-T-S dimension. All the other dimensions are SAAMI spec. But the longer L-T-S prevents the casing from stretching excessively on the 1st firing. The casing has more support, which translates to less stretching, which translates to longer case life." [/QUOTE]
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Explain How 7 PRC Has Tighter Tolerances VS 7 MM Rem Mag, without bashing any company
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