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Dirtdigger

Dirtdigger

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an article on twist rate, And I have a question. How much change in velocity would one expect to see between a 1-10" and a 1-11" twist rate barrels? Assuming barrels were the same in length and same caliber. 22" and .308". You pick a bullet.

Thanks, Derek
 
None. Each barrel is different. variation between barrels amde one after the other can be over 100 fps. Twist has no impact.

One type of rifling machine use a "sine bar" With this machine it is easy to change twist tates, so you can make a 1:20, a 1:12 and a 1:5 to make experimental barrels. I saw this experiment done with a rifled barrel with no twist.

So far as could eb determined, twist had no effect on pressure/velocity. It is an accuracy and bullet weight issue.
 
Ganderite, that is very interesting. Can you PM me with the source of that information? I definitely notice a difference in pressure/velocity on 7x57, 6.5x55 and 308 chambered barrels with different twist rates. The 308 barrels are from Ted Gaillard and have a one in twelve and a one in fifteen twist rate. The 6.5s and 7s are comparisons between commercial rifles and milsurps wth identical loads and given the variations there, the comparisons are questionable. The Gaillard barrels are a different story, both mic out at .3079 and have neither loose or tight spots. They are chambered with the same reamer, loaded with the same dies and components and show different velocities. Pressure signs seem to be comparable but I can only make a visual observation there.
 
Not enough to matter.
"...have a one in twelve and a one in fifteen..." Those would be for light for calibre bullets.
 
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