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Bullet rotation

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17 October 2012, 05:26
gwahir
Bullet rotation
What happens to the spin of the bullet. Does it slow down range with velocity reduction?
19 October 2012, 09:48
Antelope Sniper
spin actually remains relatively constant.
31 October 2012, 06:28
mdvjrp93
When the spin slow down the round starts to drift or wobble either way you know on the target.I think that you see more when it pass thru the sound barrier the second time.


1 shot 1 thrill
01 November 2012, 17:29
7mmfreak
The "wobble" is actually caused because spin stays nearly constant (Law of Conservation of Rotational Momentum) while linear momentum rapidly degrades.
15 December 2012, 23:13
wino
quote:
Originally posted by 7mmfreak:
The "wobble" is actually caused because spin stays nearly constant (Law of Conservation of Rotational Momentum) while linear momentum rapidly degrades.


What would happen if you made a custom barrel say, starting at the breach with a 1 in 6 twist, ending at the muzzle with say 1 in 13 twist, would the "forced slowing of spin" improve longer range stability?


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17 December 2012, 05:42
wino
???????


"Earth First, we'll mine the other planets later"
"Strip mining prevents forest fires"
17 December 2012, 06:40
tasco 74
quote:
Originally posted by wino:
quote:
Originally posted by 7mmfreak:
The "wobble" is actually caused because spin stays nearly constant (Law of Conservation of Rotational Momentum) while linear momentum rapidly degrades.


What would happen if you made a custom barrel say, starting at the breach with a 1 in 6 twist, ending at the muzzle with say 1 in 13 twist, would the "forced slowing of spin" improve longer range stability?


huh?????????????????????????????????????


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17 December 2012, 09:12
Fjold
Decelleration of the bullet will stop when the bullet leaves the barrel. The bullet will continue to spin at the last twist rate (relatively) in the barrel.

I have a gain twist barrel and I'm sure that my bullets don't continue to gain RPM after the bullet leaves the barrel.


Frank



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17 December 2012, 16:47
7mmfreak
quote:
Originally posted by wino:
What would happen if you made a custom barrel say, starting at the breach with a 1 in 6 twist, ending at the muzzle with say 1 in 13 twist, would the "forced slowing of spin" improve longer range stability?


I don't know of anyone who makes barrels like that. You can get gain twist. I would be inclined to go from 1-18 to 1-13 rather than from 1-6 to 1-13. I personally wonder what gain twist does to jackets (or loss twist as you propose) and how it affects drag. I know it has been around for more than a century so there are obviously those who believe in the idea.
20 December 2012, 20:13
Antelope Sniper
Wino, a declining twist barrel will not produce a balanced bullet in flight. One of the barrel makers has a write up on it, I don't remember which one, but if I remember correctly, it's one that produces rifle cut barrels, because they would have the equipement to produce them. In essence they said twist must be constant, or increasing to produce a stable bullet, but their testing did not show any accuracy benefits to an increasing twist barrel, and recommended constant twist barrels.