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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Bullet failures
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<blockquote data-quote="RockyMtnMT" data-source="post: 2414081" data-attributes="member: 7999"><p>This I believe is dead on. I have posted many times about our experience impact testing bullets and learning the relationship of stability and terminal performance. Just because a bullet is ballistically stable and shoots lights out does not mean it has enough rotational vel to perform properly on impact. There is no calculator to determine terminal stability. All I can tell us what we have concluded. I'll add that the longer a bullet is for caliber the more critical this gets. Short bullets have much less terminal performance issues. We determine min required twist for hunting with the Miller stability formula but never enter in altitude. A 1.5 sg calculated at sea level standard atmosphere is considered minimum for proper terminal performance. I personally want to see a stability factor close to 2.0 sg calculated at sea level for my personal rifles. I think it is very likely that experience of bullets changing direction after impact or not opening on impact is a result of running to low of stability. rpm's is what keeps the bullet point on after impact. If the bullet does not stay point on long enough for the bullet to fully deform it will likely change direction, tumble, or pencil.</p><p></p><p>My next chore is to add a preferred twist rate to all of our bullets along with our minimum twist that is currently listed.</p><p></p><p>When it comes to bullets that are not able to open if the impact velocity is too high. I am not sure how this could be possible. The only way to prove this theory would be to shoot this bullet into gel at high velocity and see if it will open after x inches of penetration once it has slowed enough to open. Then shoot the same bullet at lower impact velocity to see if it will open with less penetration. My experience impacting bullets is they do not have speed sensors in them. Nor do they have depth sensors telling them when it is time to open or when it is time to stop penetrating once they have reached the far side of an animal. What I do know is that a bullet that will open at xxxx fps will open more rapidly the faster the impact velocity gets. It is certainly possible to impact a bullet faster than it can handle, causing it to lose all integrity and fail to retain enough mass to continue on its directional path. I remember hearing the stories when I was young about how magnum rifles would fail to open bullets at short range and they would just zip through so fast that the bullet couldn't react quickly enough to cause damage. If this was true the bullet would expand after exiting the animal. Another campfire legend passed down through the generations. If someone can show me a test of lower velocity expanding a bullet better than high vel I will eat that crow without seasoning!</p></blockquote><p></p>
[QUOTE="RockyMtnMT, post: 2414081, member: 7999"] This I believe is dead on. I have posted many times about our experience impact testing bullets and learning the relationship of stability and terminal performance. Just because a bullet is ballistically stable and shoots lights out does not mean it has enough rotational vel to perform properly on impact. There is no calculator to determine terminal stability. All I can tell us what we have concluded. I'll add that the longer a bullet is for caliber the more critical this gets. Short bullets have much less terminal performance issues. We determine min required twist for hunting with the Miller stability formula but never enter in altitude. A 1.5 sg calculated at sea level standard atmosphere is considered minimum for proper terminal performance. I personally want to see a stability factor close to 2.0 sg calculated at sea level for my personal rifles. I think it is very likely that experience of bullets changing direction after impact or not opening on impact is a result of running to low of stability. rpm's is what keeps the bullet point on after impact. If the bullet does not stay point on long enough for the bullet to fully deform it will likely change direction, tumble, or pencil. My next chore is to add a preferred twist rate to all of our bullets along with our minimum twist that is currently listed. When it comes to bullets that are not able to open if the impact velocity is too high. I am not sure how this could be possible. The only way to prove this theory would be to shoot this bullet into gel at high velocity and see if it will open after x inches of penetration once it has slowed enough to open. Then shoot the same bullet at lower impact velocity to see if it will open with less penetration. My experience impacting bullets is they do not have speed sensors in them. Nor do they have depth sensors telling them when it is time to open or when it is time to stop penetrating once they have reached the far side of an animal. What I do know is that a bullet that will open at xxxx fps will open more rapidly the faster the impact velocity gets. It is certainly possible to impact a bullet faster than it can handle, causing it to lose all integrity and fail to retain enough mass to continue on its directional path. I remember hearing the stories when I was young about how magnum rifles would fail to open bullets at short range and they would just zip through so fast that the bullet couldn't react quickly enough to cause damage. If this was true the bullet would expand after exiting the animal. Another campfire legend passed down through the generations. If someone can show me a test of lower velocity expanding a bullet better than high vel I will eat that crow without seasoning! [/QUOTE]
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