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Posted: 2/23/2007 3:52:37 PM EDT
| "55 gr. bullets out of a 1/7 twist are slower than out of a 1/9" |
Why would a twist make a bullet slower?
+1 Even from the same barrel in the same shot string. You'd have to do a huge sample to get good statistical info. |
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I would think that you would get as much or more variation from the minute diameter differences bullet to bullet, or the bore difference barrel to barrel, and with milsurp ammo, very slight powder differences; heck, even a difference in bullet crimp could impart a microscopic difference. Assuming that ALL other things are EXACTLY the same, it stands to reason that it would take the tiniest bit more energy to spin the bullet faster. Doc |
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In theory, the faster twist-rate will use-up more energy, thus reduce velocity. However, the faster twist will retard the pressure curve, thus keeping the pressure slightly higher as the bullet travels down the bore. This latter will increase velocity. The correct answer is that the twist will have such a small effect on velocity that will be overwhelmed by bore tolerances, chamber dimensions, powder-lots, bullet dimensions, case volume, primer differences, etc. So, Each bbl. and load will behave in its own unique way. Given the exact same parameters, one kind of powder (say a slower burning rate) will give slightly higher velocities with a faster twist, while another powder (faster burning rate) will give a lower velocity when the twist is faster. Hope that confuses the issue enough to make it evident, that one cannot really tell whether or not the twist will affect velocity. Dave. |
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