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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
those who have trouble with berger
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<blockquote data-quote="elkaholic" data-source="post: 585743" data-attributes="member: 13833"><p>Twist rate is DEFINITELY a "part" of the equation. There were tests performed years ago by the military "which I have seen in my own testing", that prove this. The test were run using the M1 ('06) and the 30 carbine. The former with a 10 twist and the latter with 16 twist. Both were firing identical 110 grain bullets. The '06 was fired at longer range to simulate identical impact velocity. The bullets were fired into a ballistic gel and the wound cavities were compared. i.e. all else equal, the wound cavities should have been the same. They were anything but! The 10 twist wound cavity was greatly exaggerated in diameter and not as deep. Also proving that rotational velocity maintains itself over distance far better than forward momentum. I performed the same tests with reduced loads to simulate impact velocity with the same result. When a bullet impacts with a greater rotation, the centrifugal force causes expansion at a faster rate. This same affect is seen with thin jacketed bullets which explode in mid air given enough velocity. The velocity at which this happens is directly proportionate to rotational velocity (twist rate) all else being equal. Other factors can also affect this such as wider land three groove rifling which weakens the jacket more and is often noticed especially in smaller bores. A good example of real world damage was noticed in the old 6.5 Swede. Many people noticed they did damage beyond there bore size and velocity. This was because they had a 7.5" twist, if my memory serves me? This can be an advantage, or a disadvantage, and again, always boils down to bullet choice given the other variables indicated, and the intended use on game. As far as cut rifling vs others, I have no experience to form an opinion.......Rich</p></blockquote><p></p>
[QUOTE="elkaholic, post: 585743, member: 13833"] Twist rate is DEFINITELY a "part" of the equation. There were tests performed years ago by the military "which I have seen in my own testing", that prove this. The test were run using the M1 ('06) and the 30 carbine. The former with a 10 twist and the latter with 16 twist. Both were firing identical 110 grain bullets. The '06 was fired at longer range to simulate identical impact velocity. The bullets were fired into a ballistic gel and the wound cavities were compared. i.e. all else equal, the wound cavities should have been the same. They were anything but! The 10 twist wound cavity was greatly exaggerated in diameter and not as deep. Also proving that rotational velocity maintains itself over distance far better than forward momentum. I performed the same tests with reduced loads to simulate impact velocity with the same result. When a bullet impacts with a greater rotation, the centrifugal force causes expansion at a faster rate. This same affect is seen with thin jacketed bullets which explode in mid air given enough velocity. The velocity at which this happens is directly proportionate to rotational velocity (twist rate) all else being equal. Other factors can also affect this such as wider land three groove rifling which weakens the jacket more and is often noticed especially in smaller bores. A good example of real world damage was noticed in the old 6.5 Swede. Many people noticed they did damage beyond there bore size and velocity. This was because they had a 7.5" twist, if my memory serves me? This can be an advantage, or a disadvantage, and again, always boils down to bullet choice given the other variables indicated, and the intended use on game. As far as cut rifling vs others, I have no experience to form an opinion.......Rich [/QUOTE]
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