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Thread: 12” 308...

  1. #21
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    Jan 2014
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    Thanks for all the insights...

  2. #22
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    Jan 2014
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    Quote Originally Posted by Yondering View Post
    Suppressed lever guns are always cool.
    I've been wanting to build a F1 can that looks like an early 1900's Maxim suppressor, to match with an old lever gun for the right look. 357/38 if I can find one, but easier to find a 45 Colt.

    Twist rate - for the most part twist rate is twist rate and not dependent on barrel length, just make sure it's enough for the length of bullet you're shooting. I.e. at least 1:12 twist for most 175gr match bullets, or the standard 1:10 for heavier/longer stuff. Faster twist rate is generally unnecessary in shorter barrels unless velocity loss is extreme (like putting a 308 down into pistol velocity range) but even then the twist rate differences are pretty small. A lot of people spread the idea that twist rate should be matched to velocity, but for the most part that is incorrect.
    Yondering, not arguing, trying to learn. I thought twist rate AND velocity coupled equals RPM. Longer bullets require higher RPM for better stability. Heavier means longer in spitzer pointed bullets. So, if you slow a given bullet down (due to velocity loss from a shorter barrel) you may need a faster twist, to get RPM back up, for better stability/accuracy. I’m I looking at this wrong?

  3. #23
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    Jan 2012
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    Quote Originally Posted by 45Smashemflat View Post
    Yondering, not arguing, trying to learn. I thought twist rate AND velocity coupled equals RPM. Longer bullets require higher RPM for better stability. Heavier means longer in spitzer pointed bullets. So, if you slow a given bullet down (due to velocity loss from a shorter barrel) you may need a faster twist, to get RPM back up, for better stability/accuracy. I’m I looking at this wrong?
    A little bit, yeah, but that's really common. There is some velocity dependence, but it's still more about the twist rate than the final rpm. Even simpler than that though - give it enough twist, and forget about it. With quality modern bullets you've got a huge range of stable rpm to work with, from "just enough" to "blowing up the bullets". Consider a 1:7 twist 5.56 for example - you can shoot a 75gr bullet at 1800 fps, or at 3200 fps (with enough barrel), and it'll be stable either way. The same barrel can also be an absolute tack driver with little 50gr varmint bullets, even though a 1:7 twist is way faster than needed. The only real issues with twist rate are when a barrel isn't twisted quite fast enough for a particular bullet (like 1:9 5.56 shooting 77's, sometimes doesn't work out as well), or a really fast cartridge blowing up bullets with too much rpm (like a 22-250 with 40gr), but there's a lot of ground in between and not much need to push the edges outside of benchrest circles. IME of course.

  4. #24
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    Jan 2014
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    Makes sense. My assumption was the workable RPM for a given bullet was a tighter range. (No facts, just what I thought.)

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