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Rifles, Reloading, Optics, Equipment
Reloading
Redding competition shell holders - headspace
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<blockquote data-quote="nmbarta" data-source="post: 1520376" data-attributes="member: 78438"><p>This is true, but does not mean that rifle can't have excessive headspace if it was chambered wrong.</p><p></p><p>The go no-go gauges will still tell him if the rifle was chambered correctly.</p><p></p><p>I'm not looking to argue here at all, but my understanding of this is a little different. My experiences with belted magnums is not near as extensive as yours, but I'm not new to them by any means. I enjoy learning from the more experienced guys on this site and stand to be corrected.</p><p></p><p>There should be space in front of the shoulder on both belted and non belted cases, and while I agree that the space in front of the shoulder on a belted case is not as critical as it is on a non belted case, it can still cause problems.</p><p></p><p>When a case is improved, the neck shoulder junction is commonly moved back a few thousandths for a snug or "crushed" fit. This basically sets the headspace at zero and does not allow for forward movement or at least minimizes it. It forces the brass outward toward the chamber wall rather than forward toward the chambers shoulder.</p><p>This is also why fire forming loads can be very accurate out of ai chamberings.</p><p></p><p>It may be that some factory brass on belted cases have a little less shoulder angle than specified, in which case that would explain why the datum line can be moved forward without stretching the case wall. I don't know if this is common or not, but would make sense.</p><p></p><p>I reload for a 7rm that moves the shoulder forward .014 on the first firing, which seems a bit on the excessive side to me. It's not just the shoulder though, the case mouth moves forward almost the same amount (this is just after firing, not after sizing), this indicates to me that the entire shoulder is being pushed forward by stretching the body of the case, not blowing the shoulder outward like in an ackley improved case.</p><p></p><p>After the first firing, I trim and bump the .002. I will only fire these cases 3 times, as I have had problems with hairline cracks in the case just above the belt about 1/8", (which is where theses cases commonly fail) after sizing the 5th firing.</p><p></p><p>I believe this is due to excessive headspace which is causing the body to stretch .014 on the first firing.</p><p></p><p>Just another take on it, it's important to know what is going on. Case head separations are not fun.</p></blockquote><p></p>
[QUOTE="nmbarta, post: 1520376, member: 78438"] This is true, but does not mean that rifle can't have excessive headspace if it was chambered wrong. The go no-go gauges will still tell him if the rifle was chambered correctly. I'm not looking to argue here at all, but my understanding of this is a little different. My experiences with belted magnums is not near as extensive as yours, but I'm not new to them by any means. I enjoy learning from the more experienced guys on this site and stand to be corrected. There should be space in front of the shoulder on both belted and non belted cases, and while I agree that the space in front of the shoulder on a belted case is not as critical as it is on a non belted case, it can still cause problems. When a case is improved, the neck shoulder junction is commonly moved back a few thousandths for a snug or "crushed" fit. This basically sets the headspace at zero and does not allow for forward movement or at least minimizes it. It forces the brass outward toward the chamber wall rather than forward toward the chambers shoulder. This is also why fire forming loads can be very accurate out of ai chamberings. It may be that some factory brass on belted cases have a little less shoulder angle than specified, in which case that would explain why the datum line can be moved forward without stretching the case wall. I don't know if this is common or not, but would make sense. I reload for a 7rm that moves the shoulder forward .014 on the first firing, which seems a bit on the excessive side to me. It's not just the shoulder though, the case mouth moves forward almost the same amount (this is just after firing, not after sizing), this indicates to me that the entire shoulder is being pushed forward by stretching the body of the case, not blowing the shoulder outward like in an ackley improved case. After the first firing, I trim and bump the .002. I will only fire these cases 3 times, as I have had problems with hairline cracks in the case just above the belt about 1/8", (which is where theses cases commonly fail) after sizing the 5th firing. I believe this is due to excessive headspace which is causing the body to stretch .014 on the first firing. Just another take on it, it's important to know what is going on. Case head separations are not fun. [/QUOTE]
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Redding competition shell holders - headspace
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