# lets disccuss rate of twist

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**1****lets disccuss rate of twist**

trying to figure this out

the claim is you need x amount of twist for x amount of velocity.

and you get away with less twist if you up the velocity.

How does that work, I am not going to do the exact math but hear me out.

If say a 1-12 with a 50 gr at 2700 produces 100,000 rpm and the bullet takes x amount of time to reach target producing 300 revolutions in that time.

Now we up the velocity to 3400 fps producing 160,000 rpm and x amount of time to get to target but it will still only spin 300 times from barrel to target, its not going to spin any faster because of velocity. well yes and no.

a 1/12 twist spins once for every foot no matter what velocity its pushed at. so 300 ft to target its spun 300 times whether it was 500 ft per second or 3000 fps

so how does velocity stabalise it more ? it just gets there quicker with the same number of spins

the claim is you need x amount of twist for x amount of velocity.

and you get away with less twist if you up the velocity.

How does that work, I am not going to do the exact math but hear me out.

If say a 1-12 with a 50 gr at 2700 produces 100,000 rpm and the bullet takes x amount of time to reach target producing 300 revolutions in that time.

Now we up the velocity to 3400 fps producing 160,000 rpm and x amount of time to get to target but it will still only spin 300 times from barrel to target, its not going to spin any faster because of velocity. well yes and no.

a 1/12 twist spins once for every foot no matter what velocity its pushed at. so 300 ft to target its spun 300 times whether it was 500 ft per second or 3000 fps

so how does velocity stabalise it more ? it just gets there quicker with the same number of spins

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**2**Giant Nontypical

Join Date: Nov 2004

Posts: 5,425

I don't believe I've ever heard twist related to velocity...I have heard it related to the length of the projectile and the diameter bore...

What blows my mind is how the early gunsmiths in what is now Germany figured this all out in the mid 1500s...By the early 1700s the rate of twist for round balls was pretty standard...

What blows my mind is how the early gunsmiths in what is now Germany figured this all out in the mid 1500s...By the early 1700s the rate of twist for round balls was pretty standard...

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**4**
If say a 1-12 with a 50 gr at 2700 produces 100,000 rpm and the bullet takes x amount of time to reach target producing 300 revolutions in that time.

Now we up the velocity to 3400 fps producing 160,000 rpm and x amount of time to get to target but it will still only spin 300 times from barrel to target,

Now we up the velocity to 3400 fps producing 160,000 rpm and x amount of time to get to target but it will still only spin 300 times from barrel to target,

**its not going to spin any faster because of velocity. well yes and no.**
so how does velocity stabilize it more ? it just gets there quicker with the same number of spins

The bullet will still spin the same number of times over a given distance. That is always constant due to the barrel being constant. Excluding outside forces like air resistance which create friction on both the spin of teh bullet as well as the velocity of the bullet.

As velocity increases the RPM's increase. So, as velocity increases you will not need as high a barrel twist rate to stabilize the bullet. If a bullet needs 150,000 rpm's to be stable a barrel twist rate of 1in12 will accomplish that with 2500 fps. If the velocity is increased to 3000 fps you only need a twist rate of 1in14.4. The bullets rpm's will remain the same even though the bullet will spin less over distance.

*Last edited by bigbulls; 02-08-2010 at 07:11 PM.*

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**6**
so bigbulls, your saying that as velocity is increased centrifigul forces are greater.

Like a bicycle going 1 mph or 100 mph. the wheels still turn the same amount of rotations in 300 ft, but at 1 mph the bike wants to fall over but at 100 mph it would stay up without a rider .

I can buy that

Like a bicycle going 1 mph or 100 mph. the wheels still turn the same amount of rotations in 300 ft, but at 1 mph the bike wants to fall over but at 100 mph it would stay up without a rider .

I can buy that

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**7**Giant Nontypical

Join Date: Nov 2004

Posts: 5,425

I think you are looking at it from a velocity stand point where what you are actually talking about is the Greenhill Formula...

This states that for a given bore diameter and length of bullet there is an optimum twist rate to stabilize the bullet...It's pretty hard to spin a bullet too fast, kinda like it's hard to spin a top too fast...Too slow and it starts to wobble, too fast and it's fine...

This states that for a given bore diameter and length of bullet there is an optimum twist rate to stabilize the bullet...It's pretty hard to spin a bullet too fast, kinda like it's hard to spin a top too fast...Too slow and it starts to wobble, too fast and it's fine...

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**10**Like a bicycle going 1 mph or 100 mph. the wheels still turn the same amount of rotations in 300 ft, but at 1 mph the bike wants to fall over but at 100 mph it would stay up without a rider .

I can buy that

Does bullet weight have anything to do with it ?

LoL Like ol Larry or not he does liven things up.

*Last edited by bigbulls; 02-09-2010 at 05:19 PM.*