Effect of faster twist on short bullets
- Thread starter Mungo
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nun_hunter
Well-Known Member
In the extreme such as the 8.6 blackout extra rpm mean the bullet causes more damage when it hits its target. Whether that would be noticeable on standard short bullets in a fast twist I'm not sure but in theory they would be spinning faster so should break apart easier on impact. That would probably be good for a varmint application but wouldn't aid penetration.
Spins them faster
Frangible bullets can fragment faster in a shorter penetration distance but not enough for you to notice
The extreme end of fast twist and high velocity is the shedding of jackets in mid air
Not likely in your application
Requires velocities up above the 3500-4000 fps and very fast twists and frangible bullets with non bonded jackets
Frangible bullets can fragment faster in a shorter penetration distance but not enough for you to notice
The extreme end of fast twist and high velocity is the shedding of jackets in mid air
Not likely in your application
Requires velocities up above the 3500-4000 fps and very fast twists and frangible bullets with non bonded jackets
Heym SR20
Well-Known Member
Faster twist does make it harder to push the bullet down the barrel, so a light for calibre bullet will not achieve velocities it could achieve with a slower twist.
As in all things there is an optimum for any set of variables. If you want to shoot long heavy for calibre bullets go for a fast twist, if you want max accuracy from light bullets then go for a slower twist.
Take the old example of the 7x57. The military version, as in Boer War etc used a 1 in 7.5” or 8” twist. When Rigby started building sporting rifles they did the High Velocity shooting a 140gn bullet and many have a slower twist.
The American 7-08 was designed for 140gn bullets and the 1 in 10” twist rate is standard.
As in all things there is an optimum for any set of variables. If you want to shoot long heavy for calibre bullets go for a fast twist, if you want max accuracy from light bullets then go for a slower twist.
Take the old example of the 7x57. The military version, as in Boer War etc used a 1 in 7.5” or 8” twist. When Rigby started building sporting rifles they did the High Velocity shooting a 140gn bullet and many have a slower twist.
The American 7-08 was designed for 140gn bullets and the 1 in 10” twist rate is standard.
Heym SR20
Well-Known Member
This article gives most of the answers
Theoretically this is correct
But its not relevant
Never likely to impact velocity in any significant capacity
I have run 1:8” 30 cal bullets at as much as 3350fps from a 24” barrel
Have run 40gr bullets at 3400fps in a .222
No shortage of velocity potential because of the faster twist
Then its ****ed or the ammo is crap….
jthyttin
Well-Known Member
Neither the discussion nor linked article touched on the most important issue.
- no bullet is perfect
- faster you spin a bullet, effects caused by imperfections get more pronounced
So higher quality bullets (and barrels) suffer less from "too fast" twist.
And another point, if you want your bullet to travel in straight line in terminal media (like not changing direction when it hits deer), "over stabilized" is way better than "marginally stabilized". There are some discussion on LR shooting and "less than optimal" stabilization but I think currently most believe it's non-issue. Generally bullet velocity decreases a lot faster (like order of magnitude or close) than RPM, so a bullet that is stable at muzzle should continue be stable until it hits transsonic region (what happens there depends on bullet). But I seem to remember some conflicting evidence even there. Haven't paid much attention lately.
- no bullet is perfect
- faster you spin a bullet, effects caused by imperfections get more pronounced
So higher quality bullets (and barrels) suffer less from "too fast" twist.
And another point, if you want your bullet to travel in straight line in terminal media (like not changing direction when it hits deer), "over stabilized" is way better than "marginally stabilized". There are some discussion on LR shooting and "less than optimal" stabilization but I think currently most believe it's non-issue. Generally bullet velocity decreases a lot faster (like order of magnitude or close) than RPM, so a bullet that is stable at muzzle should continue be stable until it hits transsonic region (what happens there depends on bullet). But I seem to remember some conflicting evidence even there. Haven't paid much attention lately.
at what distance, please say 500 yards and not 100 yard,
The only risk is with very fast twist at higher speeds . Used to happen in open class the bullet never got near the target and the shooter sometimes caught the visual in the scope , its not predictable and or repeatable with any true certainty round after round in my experience. climate must be a big factor
I have used 308's with 1in10 and 1in14, I always thought the 1in10 hit the deer harder with the same bullet.
Bullets follow a parabolic type curve, at long range they need to follow the trajectory or they start to fly sideways if to fast a twist is used. That's an issue for the target shooters, not for hunters.
Bullets follow a parabolic type curve, at long range they need to follow the trajectory or they start to fly sideways if to fast a twist is used. That's an issue for the target shooters, not for hunters.
Do you mean spin drift?
Whereby the spin of the bullet imparts a force on the bullet that sees it “climb” marginally up and to the left or right depending on barrel twist and spin direction?
I haven’t tried lighter
Ah!
So this may not be a ‘length of bullet issue’ so much as a ‘particular loading’ issue.
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