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Rifles, Reloading, Optics, Equipment
Reloading
Neck tension and max bullet grip force
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<blockquote data-quote="MagnumManiac" data-source="post: 2136529" data-attributes="member: 10755"><p>This is my understanding of what occurs upon firing a cartridge through testing with firing a cartridge with just a primer in an oversized barrel.</p><p>Firstly, the primer pressure is enough to expand a neck and the bullet is fired at quite some velocity out of the oversized barrel.</p><p>Upon measuring the neck before firing and after, it is obvious that the bullet is not held for any length of time other than the time it takes for the neck to expand. There are no drag marks on the bullets surface, which indicated very little, if any, movement occurs prior to the neck expanding.</p><p>The neck would move on average .001"-.0015" larger, which is why I believe the spring back amount is all the bullet is held with.</p><p>I also tried crimping the bullet, 9 out of 10 bullets failed to straighten the case mouth completely and all were faster than non-crimped bullets.</p><p>This is why factory bullets are crimped, it increases start pressure and reaches a gentler curve under MAP, hence why factory fodder works in so many different firearms.</p><p>So, the conclusion is this:</p><p>Bullets do not get held upon firing as many think. As soon as the bullet is released of the neck, there is no tension, the neck simply expands and the bullet is free to travel. A crimp delays this by milliseconds as the brass takes longer to expand and release the bullet. There is virtually zero bullet movement before the neck expands enough, maybe a couple of 10 thousandths, and the bullet is released.</p><p>When you pull bullets, you can feel that first resistance, you can also feel that the tension has changed as soon as the bullet moves. If you re-seat a bullet in a case that has had a bullet pulled from it, you also see that the neck tension is not the same.</p><p>The only difference to this in a guns chamber is the gas pressure forcing the neck into the space provided.</p><p></p><p>Anyway, that's my own conclusion from testing my theories. As I have had bullets do strange things and wanted to know why.</p><p></p><p>Cheers.</p></blockquote><p></p>
[QUOTE="MagnumManiac, post: 2136529, member: 10755"] This is my understanding of what occurs upon firing a cartridge through testing with firing a cartridge with just a primer in an oversized barrel. Firstly, the primer pressure is enough to expand a neck and the bullet is fired at quite some velocity out of the oversized barrel. Upon measuring the neck before firing and after, it is obvious that the bullet is not held for any length of time other than the time it takes for the neck to expand. There are no drag marks on the bullets surface, which indicated very little, if any, movement occurs prior to the neck expanding. The neck would move on average .001”-.0015” larger, which is why I believe the spring back amount is all the bullet is held with. I also tried crimping the bullet, 9 out of 10 bullets failed to straighten the case mouth completely and all were faster than non-crimped bullets. This is why factory bullets are crimped, it increases start pressure and reaches a gentler curve under MAP, hence why factory fodder works in so many different firearms. So, the conclusion is this: Bullets do not get held upon firing as many think. As soon as the bullet is released of the neck, there is no tension, the neck simply expands and the bullet is free to travel. A crimp delays this by milliseconds as the brass takes longer to expand and release the bullet. There is virtually zero bullet movement before the neck expands enough, maybe a couple of 10 thousandths, and the bullet is released. When you pull bullets, you can feel that first resistance, you can also feel that the tension has changed as soon as the bullet moves. If you re-seat a bullet in a case that has had a bullet pulled from it, you also see that the neck tension is not the same. The only difference to this in a guns chamber is the gas pressure forcing the neck into the space provided. Anyway, that’s my own conclusion from testing my theories. As I have had bullets do strange things and wanted to know why. Cheers. [/QUOTE]
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Neck tension and max bullet grip force
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