sprint;3736346 My current believe then is that a given bullet weight and length will have a rotational velocity threshold below which it will no longer remain gyroscopically stable if it falls below that value anywhere within the total duration of bullet flight....[/QUOTE said:
5.56-223 from 10.5 inch Barel
- Thread starter carlchevalier
- Start date
One of the problems with the error net is that it never qualifies the poster, I didn't know you from a hole in the ground and still don't - my crystal ball is in the shop getting polished. In 9 out of 10 cases where someone makes a post like yours, what I posted is applicable. I stand by my post, 90 percent of the time it is valid, and no you obviously did not mention that you are an experienced shooter with AR's - that type of "detail" would have been helpful.
Rpm
I didnt say that barrel length has anything to do with twist rate, just that all the AR twist rate bullet weight data was determined with full length barrels.
How do uber shorty revolvers stabilize bullets ? They dont - not fully. Why do you not see uber shorty barrels in target competitions?
More spin - Higher RPM or rotational velocity. What is "full rotational velocity" ? I assume it is the ideal spin to maximize stability not the spin required to prevent the jacket from getting torn to bits.
Doesnt the number of rotations before the bullet leaves the barrel determine the rotational velocity, RPM or spin?
Given a 10 inch barrel and a 20 inch barrel with the same twist rate excluding other factors - would the RPM, rotational velocity or spin be the same ?
I didnt say that barrel length has anything to do with twist rate, just that all the AR twist rate bullet weight data was determined with full length barrels.
How do uber shorty revolvers stabilize bullets ? They dont - not fully. Why do you not see uber shorty barrels in target competitions?
More spin - Higher RPM or rotational velocity. What is "full rotational velocity" ? I assume it is the ideal spin to maximize stability not the spin required to prevent the jacket from getting torn to bits.
Doesnt the number of rotations before the bullet leaves the barrel determine the rotational velocity, RPM or spin?
Given a 10 inch barrel and a 20 inch barrel with the same twist rate excluding other factors - would the RPM, rotational velocity or spin be the same ?
Thank you.
Barrel length is irrelevant. If the barrel has a 1:12 twist, the bullet will make one revolution for every 12" it travels. Once the bullet has fully engaged the rifling, the rotation is established. If the twist is 1:12, it doesn't matter if the barrel gives one, two or three full revolutions to the bullet before the bullet exits. The bullet receives the same rotation.
Barrel length and velocity are linked, of course.
Target pistols often have longer barrels because of sight radius. Some very sophisticated, very accurate, target pistols do have rather short barrels - the ones with the magazine in front of the trigger are examples of the style. Put a short barrelled pistol in a machine rest, and the actual grouping ability can be determined. Barrel length isn't much of a factor.
Nope. Rotational velocity does not drop with forward velocity. Thus a supersonic bullet becomes more stable the further it flies.
Back in the 50's Hatcher did some experiments where he fired bullets straight up. what he found was they tended to fall back to earth base first. Even though the bullet had literally come to a stop at its apogee, the thing had continued to spin and retained its stability.
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So - Barrel length is irrelevant ? A longer barrel is not more accurate than a short barrel ?
- a snub nose 38 will be as accurate as a long barrel target 38.
Funny that snubbies are not use in target competitions.
So - it doesnt matter if the bullet gets one two or three revolutions before exiting
- it will spin the same.
Funny how a toy spinning top is not very stable with a spin from a very short string and stops quickly, yet with a long pull it goes and goes before falling .
So - Barrel length is irrelevant ? A longer barrel is not more accurate than a short barrel ?
- a snub nose 38 will be as accurate as a long barrel target 38.
Funny that snubbies are not use in target competitions.
So - it doesnt matter if the bullet gets one two or three revolutions before exiting
- it will spin the same.
Funny how a toy spinning top is not very stable with a spin from a very short string and stops quickly, yet with a long pull it goes and goes before falling .
The twist rate of the rifling and the velocity of the bullet are the determining factors in the spin rate of the bullet. Barrel length has zip to do with it.
Given a specific twist rate, lets say 1:10, why do you think a 20" barrel would impart a faster spin rate than a 1:10 barrel that is only 10" long? 1:10 is 1:10 regardless of barrel length.
Bull####! The two are only linked while the bullet is inside the barrel. Once it leaves the barrel, forward velocity and spin rate are not linked in any way. Bullets lose accuracy at very long range because they pas through the transonic velocity range and are subjected to buffeting from the sonic shockwaves moving along the bullet.
Bull####! I have shot ultra short barreled revolvers and never saw any evidence of keyholing. Short barreled revolvers are not generally used in competition because the short sight radius limits accuracy.
WOW! It just amazes me we have to have these same conversations over and OVER and OVER again. Do some reading on this site would you.
Barrel length generally has no effect on accuracy. When using iron sights, as in a target pistol, the sight radius makes the difference because it allows the sights to be aligned more finely. This is completely irrelevant to the mechanical accuracy of the firearm's ability to group shots closely together.
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You misunderstand - I never said or implied twist rate is determined by barrel length. I never said or implied a 20 " barrel imparts a faster twist rate.
As far as uber short barrels - keyholing was not the issue in the post, accuracy from bullet stability was the topic.
Long barrels rather than short barrels are used in target competition not because of site radius but because the short barrels do not have enough length to give the bullet a full spin sufficient for accuracy as well as optimum velocity.
So - a bullet in a 1 in 9 ten inch AR gets a full spin , a 1 in 9 twenty inch 2 spins, but in a one in 7 twist AR less than a 1 spin. Less than ideal for stabilization.
Like a toy top - gyroscopic stability - more spins more stable.
You misunderstand - I never said or implied twist rate is determined by barrel length. I never said or implied a 20 " barrel imparts a faster twist rate.
As far as uber short barrels - keyholing was not the issue in the post, accuracy from bullet stability was the topic.
Long barrels rather than short barrels are used in target competition not because of site radius but because the short barrels do not have enough length to give the bullet a full spin sufficient for accuracy as well as optimum velocity.
So - a bullet in a 1 in 9 ten inch AR gets a full spin , a 1 in 9 twenty inch 2 spins, but in a one in 7 twist AR less than a 1 spin. Less than ideal for stabilization.
Like a toy top - gyroscopic stability - more spins more stable.
because a longer barrel give higher velocity by increasing the time period of energy transfer to the bullet. The faster a particle spirals within the barrel, the more angular momentum it gains.
There are two factors here - the twist rate and velocity of the body in the axis of the rotation. The angular velocity of bullet depends on how "much" of the velocity of the bullet along the axis of rotation being translated by the rifling. You can have high velocity along the axis with a "slow" translator, or a low velocity with a "fast" translator.- and remember energy loss by fiction. So obviously having a super low velocity with a super fast twist rate won't work.
At the end of the day, more doesn't mean better. You only need so much spin to stay stable for a certain density of medium(air) - that opens up a full graduate topic of study and some dude can probably write a thesis out of it....
I think you're missing the point. Regardless of how much barrel there is, the RPM is determined by the twist rate and initial velocity. Longer barrels provide for higher velocities which imparts a higher RPM. The length of the barrel and the twist rate together do not affect RPM.
TDC
It is the "rate" that matter, not the distance.
I can push you in one director for 1 one second, or push your for 10 seconds.
Either way, as long as I push you in one direction, you are still going to the same direction irregardless how long I am going to push you.
Now, break the velocity vecotor down into components that are perpendicular to the axis of rotation and the direction of rifling.
I can push you in one director for 1 one second, or push your for 10 seconds.
Either way, as long as I push you in one direction, you are still going to the same direction irregardless how long I am going to push you.
Now, break the velocity vecotor down into components that are perpendicular to the axis of rotation and the direction of rifling.
