The longer a bullet gets, the more sensitive to/strict the bullet is as far as twist rate is concerned. Stubby/barrel shaped bullets for a given weight class are very forgiving with twist requirements. Plastic tips also don't increase the need for faster twist as much as their greater length suggests...i.e. a 1.0" OTM has a higher twist twist requirement than a 1.0" BlitzKing.
And don't forget the longer the bullet, the less bearing surface the bullet has, and the higher twist rates necessary to stablize actually hurt mechanical accuracy. It is worth it because of the improved ballistics, but it is a 2 edge sword. For mechanical accuracy, you actually want the opposite, as slow a twist rate as possible to still stabilize the bullet, and the center of gravity as close to the center of pressure as possible.
What typically establishes the angle of attack of the bullet? Does it tend to change pitch at all during flight? I'd recently been wondering about this after watching a few (very) high speed videos where the bullet clearly had an angle of attack that didn't match the flight path. This is the first time i'd seen it even partially explained in a video.
jcims The initial angle of attack comes in part due to the fact that gravity is always pulling objects downwards and so we must angle the barrel upwards to arc the projectile to the target. There are also a wide range of aerodynamic forces acting on the bullet. See the diagram in the video around the 30 second mark and think of the center of gravity as a fulcrum point which the projectile body naturally wants to rotate around. The center of pressure is the point equivalent location for the average pressure distribution. If the center of pressure is in front of the center of gravity and pushing upwards, it will cause the bullet to pitch upwards (note that in many ballistics books they refer to change in roll, pitch, and yaw ...as simply yaw.). If there is a present crosswind this will also cause a vertical shift in the bullets position which is described as the magnus effect. The pitch does change during flight. The fact that a bullet spins means that it undergoes precession and nutation. Aerodynamic forces also change. This change is most apparent when a bullet transitions from the supersonic to subsonic regimes. The center of pressure can rapidly shift as the shock waves dissipate and in some cases cause the bullet to tumble. I hope this helped.
@@donttreadonme1423 that is a fantastic explanation with some bonus material. The AOA part of it i worked out myself but i hadn't given too much thought to the transonic tumbling and the gyroscopic precession part of it. I belive you nailed it!
@@donttreadonme1423 Ayant été en bureau d'études du FAMAS (à la Manufacture Nationale d'Armes de Saint Etienne, Loire, France entre 1969 et 1994), j'ai pu consulté une photo à très haute vitesse de la balle de 5,56 à la sortie du canon : c'est irréaliste ! La balle est pratiquement perpendiculaire à sa trajectoire...Personne ne peut croire cela et pourtant c'est la vérité !
In most situations, the barrel can either have a right hand twist or a left hand twist. The only place this makes any difference is in precision long-distance (>300yds) competitions where spin drift comes into play. Even then, a good ballistics calculator will give you a holding solution to account for left or right twists in the rifling (along with twist rate). Mathematically speaking, due to the Coriolis Effect rifling in the northern hemisphere does differ from the southern hemisphere. Granted, that's in the void of paper, not the real world, and the effect is negligible in practice. As for the "why", mostly tradition and marketing. Some manufacturers will state that with large caliber rifles, right-handed shooters should have left twist rifling to torque the stock away from the cheek to lessen felt recoil. Ehhhhhhhh.. yeah, I don't buy into that much. Generally speaking, it's not of any consequence unless you're a nationally/world ranked precision shooting specialist in the 1000yd+ category.
@@TheMrMused Il existe TROP d'empirisme chez les pratiquants du tir et pas assez de connaissance de la balistique intérieure, extérieure et terminale !
Most barrels have RH twist rifling lands and grooves. However, almost all barrels in 45 ACP have LH twists. My old Colt Woodsman (22LR) and SAA Colt 45 have LH twist rifling. I don't think it matters. My two Kimbers in 45 ACP have LH twists. But my Tommy gun in 45 ACP has RH twist.
Avec un pas des rayures de 9 pouces soit 23 cm pour un tour, une 5,56 x 45 Otan sort du canon à une vitesse initiale de presque 1000 mètres par seconde...donc 1000 / 0,25* = 4000 tours pas seconde ou 240 000 tours par minute ! * pour la facilité du calcul mental !
@@excellenceetserenite9541 I beg You pardon, but I do not speak French. Pardonnez moi, ma je ne parlair pas de francoise! (I don't even know if I spelled that correctly! 😃). PS. Best Regards & have a nice day! :)
I do not agree with the assumption of flight, the bullet flight is not along sight path like you depicted and certainly not at an angle that is not aligned with pathway it is on! The bullet is spinning along an arching pathway alway aligned with its path rising above the line of sight and descending back into line of sight always aligned with its flight path at the target. The depiction is incorrectly assumed and if were true......very rarely would anyone hit a target they intended to hit.
You're confusing flight path with point of aim. A bullet 'falls' rather than 'flies', so it is never a straight path. And that has nothing to do with stability.
Faux ! Sauf au stand de tir où le tube essayé est horizontal sur l'affût d'essai, le vecteur vitesse initiale du projectile en sortie de la bouche du canon, tangent à une parabole, est incliné de l'angle de hausse ! L'angle de la visée a une distance donnee tient compte de cet angle calcule dans les tables de gir de la cartouche !
very great graphics for a great explanation, thanks
Great explanation, thank you
The longer a bullet gets, the more sensitive to/strict the bullet is as far as twist rate is concerned. Stubby/barrel shaped bullets for a given weight class are very forgiving with twist requirements. Plastic tips also don't increase the need for faster twist as much as their greater length suggests...i.e. a 1.0" OTM has a higher twist twist requirement than a 1.0" BlitzKing.
Which bullet weight would you recommend for 1.12 twist rate on my 270 win. For long distance shooting . Thx
Go to Berger bullet twist calculator.
And don't forget the longer the bullet, the less bearing surface the bullet has, and the higher twist rates necessary to stablize actually hurt mechanical accuracy. It is worth it because of the improved ballistics, but it is a 2 edge sword. For mechanical accuracy, you actually want the opposite, as slow a twist rate as possible to still stabilize the bullet, and the center of gravity as close to the center of pressure as possible.
What typically establishes the angle of attack of the bullet? Does it tend to change pitch at all during flight?
I'd recently been wondering about this after watching a few (very) high speed videos where the bullet clearly had an angle of attack that didn't match the flight path. This is the first time i'd seen it even partially explained in a video.
jcims The initial angle of attack comes in part due to the fact that gravity is always pulling objects downwards and so we must angle the barrel upwards to arc the projectile to the target. There are also a wide range of aerodynamic forces acting on the bullet. See the diagram in the video around the 30 second mark and think of the center of gravity as a fulcrum point which the projectile body naturally wants to rotate around. The center of pressure is the point equivalent location for the average pressure distribution. If the center of pressure is in front of the center of gravity and pushing upwards, it will cause the bullet to pitch upwards (note that in many ballistics books they refer to change in roll, pitch, and yaw ...as simply yaw.). If there is a present crosswind this will also cause a vertical shift in the bullets position which is described as the magnus effect. The pitch does change during flight. The fact that a bullet spins means that it undergoes precession and nutation. Aerodynamic forces also change. This change is most apparent when a bullet transitions from the supersonic to subsonic regimes. The center of pressure can rapidly shift as the shock waves dissipate and in some cases cause the bullet to tumble. I hope this helped.
@@donttreadonme1423 that is a fantastic explanation with some bonus material.
The AOA part of it i worked out myself but i hadn't given too much thought to the transonic tumbling and the gyroscopic precession part of it.
I belive you nailed it!
@@donttreadonme1423 Ayant été en bureau d'études du FAMAS (à la Manufacture Nationale d'Armes de Saint Etienne, Loire, France entre 1969 et 1994), j'ai pu consulté une photo à très haute vitesse de la balle de 5,56 à la sortie du canon : c'est irréaliste ! La balle est pratiquement perpendiculaire à sa trajectoire...Personne ne peut croire cela et pourtant c'est la vérité !
What bullet and load for a 7mm- 08 with 1:9.5 twist and a 20 inch barrel
150 OR 140
question : can the bullet overtwist? is there a thing called overtwisting for bullets ?
Sous quelqu'effort que ce soit, tout se déforme !
Does a bullet turn to the right or the left and why ? Do different barrels twist the groves in different directions ?
In most situations, the barrel can either have a right hand twist or a left hand twist. The only place this makes any difference is in precision long-distance (>300yds) competitions where spin drift comes into play. Even then, a good ballistics calculator will give you a holding solution to account for left or right twists in the rifling (along with twist rate). Mathematically speaking, due to the Coriolis Effect rifling in the northern hemisphere does differ from the southern hemisphere. Granted, that's in the void of paper, not the real world, and the effect is negligible in practice. As for the "why", mostly tradition and marketing. Some manufacturers will state that with large caliber rifles, right-handed shooters should have left twist rifling to torque the stock away from the cheek to lessen felt recoil. Ehhhhhhhh.. yeah, I don't buy into that much.
Generally speaking, it's not of any consequence unless you're a nationally/world ranked precision shooting specialist in the 1000yd+ category.
@@TheMrMused Il existe TROP d'empirisme chez les pratiquants du tir et pas assez de connaissance de la balistique intérieure, extérieure et terminale !
@@excellenceetserenite9541 Tout à fait d'accord !
Most barrels have RH twist rifling lands and grooves. However, almost all barrels in 45 ACP have LH twists. My old Colt Woodsman (22LR) and SAA Colt 45 have LH twist rifling. I don't think it matters. My two Kimbers in 45 ACP have LH twists. But my Tommy gun in 45 ACP has RH twist.
...250 thousand rpm's?...
Yeah I knew bullets spin but never thought they do it THAT FAST!
Avec un pas des rayures de 9 pouces soit 23 cm pour un tour, une 5,56 x 45 Otan sort du canon à une vitesse initiale de presque 1000 mètres par seconde...donc 1000 / 0,25* = 4000 tours pas seconde ou 240 000 tours par minute !
* pour la facilité du calcul mental !
@@excellenceetserenite9541 I beg You pardon, but I do not speak French. Pardonnez moi, ma je ne parlair pas de francoise! (I don't even know if I spelled that correctly! 😃).
PS. Best Regards & have a nice day! :)
@@excellenceetserenite9541 PS.2 > If you'd like we could continue in Polish or Italian! 😂 ...although - SORRY! - no French! 🙂
Facing left now attacking the base 🤣 daddy cool, but papyrus fool 🙀
PS. Simple & to the point. Thank you.
Pointless oversimplification.
anyone forensic medicine student
I do not agree with the assumption of flight, the bullet flight is not along sight path like you depicted and certainly not at an angle that is not aligned with pathway it is on!
The bullet is spinning along an arching pathway alway aligned with its path rising above the line of sight and descending back into line of sight always aligned with its flight path at the target.
The depiction is incorrectly assumed and if were true......very rarely would anyone hit a target they intended to hit.
Poi
You're confusing flight path with point of aim.
A bullet 'falls' rather than 'flies', so it is never a straight path. And that has nothing to do with stability.
Faux ! Sauf au stand de tir où le tube essayé est horizontal sur l'affût d'essai, le vecteur vitesse initiale du projectile en sortie de la bouche du canon, tangent à une parabole, est incliné de l'angle de hausse ! L'angle de la visée a une distance donnee tient compte de cet angle calcule dans les tables de gir de la cartouche !