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
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...
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.
Yes, the bullet spins faster because RPM's is revolutions per minute which is a measurement of time, not distance.
Quote:
so how does velocity stabilize it more ? it just gets there quicker with the same number of spins
The bullet is more stable because as the the RPM's increase the centrifugal force around the axis of the bullet increases. Think about a top spinning. The higher the RPM's the more stable the top becomes even though it isn't moving over distance any faster.
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.
__________________
"The danger to America is not Barack Obama but a citizenry capable of entrusting a man like him with the Presidency........... Blaming the prince of the fools should not blind anyone to the vast confederacy of fools that made him their prince. The Republic can survive a Barack Obama, who is, after all, merely a fool. It is less likely to survive a multitude of fools such as those who made him their president."
I asked this same question concerning a .30-06 which people claim can shoot everything from 55gr bullets to 225 gr bullets.
Where is "Relentless" when you need him.............Larry !!!
__________________
Silence is Acceptance. "To stand in silence when they should be protesting makes cowards out of men." ~ Abraham Lincoln ~ Stand Up and Be Counted !
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
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...
Can any rifle shoot a 55 gr bullet and 225 gr bullet well ?
Will either end of the spectrum tumble and keyhole a target ?
__________________
Silence is Acceptance. "To stand in silence when they should be protesting makes cowards out of men." ~ Abraham Lincoln ~ Stand Up and Be Counted !
sheridan, a standard 30/06 is a 1/10 twist, a 55 gr 224 diameter bullet will stabilize in a 1/10 twist also at around 3100 fps. that .224 bullet will stabilize at 223 rem velocities with a 10 twist, the same bullet will stabilize out of a 14 twist at 22/250 velocities. So MV, length and diameter all matter. weight does'nt matter its length, dead coyote makes 70 gr bullets the same length as an average 55 gr and stabilise the same as a 55 gr.
Now once you get a bullet stabilized, you can't spin it too fast till you overspin it to the point that the jacket shreds shortly after exiting the muzzle, accuracy may be a bit better with the optimum twist for that bullet but you'll haveta measure it.
fast twists also have an advantage when it comes to terminal performance, spin helps expansion also.
RR
__________________
Born To Hunt, Forced To Work.
Last edited by Ridge Runner; 02-09-2010 at 01:15 PM.
lets disccuss rate of twist
