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Rifles, Reloading, Optics, Equipment
Reloading
Bumping shoulders
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<blockquote data-quote="Bart B" data-source="post: 643876" data-attributes="member: 5302"><p>Having worn out one 26 caliber and three and a half 30 caliber belted magnum barrels in competition, using full length sizing dies set to bump the fired case shoulder back a couple thousandths has always given long case life and excellent accuracy at long range. Brand new cases have produced the same level of accuracy of no worse than 6/10ths MOA at 1000. Sometimes, I've turned case necks to uniform their thickness, but if new cases have no more than 1/1000th spread in neck wall thickness, they aren't turned.</p><p></p><p>I've never had a problem with that so-called donut at the back of the neck at the shoulder. If it was there, its effect wasn't enough to cause problems. Maybe it was not an issue as my chamber necks were at SAAMI spec allowing a lot of room around the loaded round's case neck. Never used those tight-neck chambers so enamored by many.</p><p></p><p>Biggest issue with belted cases I've seen is caused by case headspace (distance between head and belt front) is typically a few to several thousandths less than the chamber headspace of .220 inch or more. That allows a ridge a few thousandths long to form right in front of the belt when a new case is fired. And that ridge prevents consistant case fit at the back end of the chamber when it's normally resized. Folks used to cut the bottom and top off a standard full length sizing die, square its bottom, then set that die up in the press such that a previously full length sized case could be sized again all the way to where the botton of that die sized the ridge in front of the belt back down to virtual new case diameter. Chambering these "double sized" cases was done without accuracy robbing interference. Nowadays, Larry Willis Innovative Collet Die's do the same thing.</p></blockquote><p></p>
[QUOTE="Bart B, post: 643876, member: 5302"] Having worn out one 26 caliber and three and a half 30 caliber belted magnum barrels in competition, using full length sizing dies set to bump the fired case shoulder back a couple thousandths has always given long case life and excellent accuracy at long range. Brand new cases have produced the same level of accuracy of no worse than 6/10ths MOA at 1000. Sometimes, I've turned case necks to uniform their thickness, but if new cases have no more than 1/1000th spread in neck wall thickness, they aren't turned. I've never had a problem with that so-called donut at the back of the neck at the shoulder. If it was there, its effect wasn't enough to cause problems. Maybe it was not an issue as my chamber necks were at SAAMI spec allowing a lot of room around the loaded round's case neck. Never used those tight-neck chambers so enamored by many. Biggest issue with belted cases I've seen is caused by case headspace (distance between head and belt front) is typically a few to several thousandths less than the chamber headspace of .220 inch or more. That allows a ridge a few thousandths long to form right in front of the belt when a new case is fired. And that ridge prevents consistant case fit at the back end of the chamber when it's normally resized. Folks used to cut the bottom and top off a standard full length sizing die, square its bottom, then set that die up in the press such that a previously full length sized case could be sized again all the way to where the botton of that die sized the ridge in front of the belt back down to virtual new case diameter. Chambering these "double sized" cases was done without accuracy robbing interference. Nowadays, Larry Willis Innovative Collet Die's do the same thing. [/QUOTE]
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