Tuesday Trivia: Can You Over-Stabilize a Bullet?
On the Applied Ballistics Facebook page a few seasons ago, Ballistician Bryan Litz posed a “Tuesday Trivia” question about ballistics. This being Tuesday we thought we’d bring back this interesting brain-teaser — a true/false question about bullet stabilization. On shooting forums you often find heated arguments about “over-stabilization”. Bryan wants readers to consider the issue of over-stabilization and answer a challenge question…
Is This Statement TRUE or FALSE?
“The problem with ‘over-stabilizing’ a bullet (by shooting it from an excessively fast twist rate) is that the bullet will fly ‘nose high’ on a long range shot. The nose-high orientation induces extra drag and reduces the effective BC of the bullet.”
True or False, and WHY?
Click the “Post Comment” link below to post your reply (and explain your reasoning).
Diagram from the University of Utah Health Sciences Library Firearm Ballistics TutorialBullet Movement in Flight — More Complicated Than You May Think
Bullets do not follow a laser beam-like, perfectly straight line to the target, nor does the nose of the bullet always point exactly at the point of aim. Multiple forces are in effect that may cause the bullet to yaw (rotate side to side around its axis), tilt nose-up (pitch), or precess (like a spinning top) in flight. These effects (in exaggerated form) are shown below:Yaw refers to movement of the nose of the bullet away from the line of flight. Precession is a change in the orientation of the rotational axis of a rotating body. It can be defined as a change in direction of the rotation axis in which the second Euler angle (nutation) is constant. In physics, there are two types of precession: torque-free and torque-induced. Nutation refers to small circular movement at the bullet tip.
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- Over-Stabilization of Bullets — Why Is Too Much Spin a Problem?
- Tuesday Trivia Challenge from Bryan Litz, Ballistics Guru
- Bullet Stability and Barrel Twist Rates — What You Need to Know
- How Do Bullets Fly — Great Online Resource Explains Key Factors
- “How Do Bullets Fly” — Great Online Resource with Smart Science
Tags: ballistics, Brain-Teaser, Bryan Litz, Bullet Stabilization, Spin Stabilization, Tuesday Trivia
Ok, no-one else is brave enough to have a go and not being on FB, I don’t know the answer. I’m guessing it’s false- the issue of over-stabilization seems to be wildly exaggerated. The other forces acting on the bullet, wind especially, have a far greater effect on its course. From a practical point of view, the risk of driving “short” bullets at high velocity through tight twists are that thin jackets may come apart and it takes more pressure to achieve the same velocity.
False
Reason- Just because- like my mother used to tell me!
Theoretically yes.
Taking the question to its limit, with an infinite twist rate all the linear momentum will turn into angular momentum and the bullet will take an infinite amount of time to get out of the barrel.
False
you can not over stabilize a bullet in flight, you can spin the jacket off a bullet which causes it to fail. That is a bullet failure not a stabilization problem.
True.
False, bullet will not consistently fly tip high from being over stabilized.
Yes, but not trivial only at long ranges. Theoretically, at peak altitude on the trajectory parabola, if the bullet does not tip point first into the downward leg, the BC and other factors will dramatically change and the circle of impact will be dramatically enlarged.
Statement is true.
Over-stabilized means that the projectile stays pointing at the angle it is launched at, rather than the nose following the trajectory.
This means the bullet flies nose up at the end of it’s flight increasing it’s drag. Longer flight time than an optimally spun bullet, so more wind drift, and elevation required.
False.
Small arms bullets will ‘trace’ with the trajectory regardless of stability factor.
The myth of over-stabilization likely comes from large caliber artillery guns with very high angles of fire. Occasionally with those projectiles which way 100’s of pounds, and are launched over 30 degrees, they reach heights where the air is thin, and the projectile velocity at apogee is slow (very low dynamic pressure to orient the projectile) and the moment of inertia is so high (a lot of spinning mass) that such a projectile can ‘fail to trace’, and fall to the ground base first. This would cause the round to fall short (possibly on friendly forces vs. the enemy) and likely fail to fuse (round needs to impact point first for an impact fuse to detonate the round).
But there are a lot of differences with small arms. Bullets are much lighter, don’t slow down at apogee, don’t get that high, etc. In fact, the more stable a bullet is, the better it will keep its axis aligned with the flight path.
Academics aside, live fire radar tracks of small arms rounds show reduced drag for all speeds, especially transonic, for bullets fired from faster twist rates, all else equal. This includes on the downrange (falling) portion of the trajectory.
Thanks for bringing this back, it’s been a while since we did trivia!
-Bryan
True. From my research it causes the bullet to fail to track the nose on course of the trajectory and you have the bullet falling horizontal rather than more vertical, you want it to keep tracking like a missile, not like a Football.
I would have thought the article would have answered the question, instead of just creating another discussion.
Post the correct answer, please.
You use the name Bryan Litz and people expect to have an answer.
Very fast twist rates can spin the occasional projectile till it breaks up. If you are willing to accept that and the miss from time to time then go ahead.
I think that physics doesn’t change between small arms and artillery shells, it is just a matter of how much an effect has influence on the physic system.
It is undoubtful that an object with higher gyroscopic momentum will try to keep the initial attitude, which would ideally coincide with the barrel line. This means that at very long ranges, whrere the drops are higher and barrels are pointing “up” to compensate, the bullet will fly with a certain amount of angle of attack that could cause detrimental effects on the drag coefficient. Obviously this could have a very little effect if the angle is small (as reported in previous answers), but it will be there.
So, in my opinion, you can over stabilize a small arm projectile, but its effect will be very limited.
I guess that the over stabilization will always happen even for small arms, it is just a matter of how much this effect can be seen on the bullet trajectory.
Physics doesn’t change for small arms or artillery: a rotating body will have a gyroscopic effect that will try to keep the initial orientation. This means that also for small arms at the end of the trajectory the bullet will be flying with a certain angle of attack that will influence the drag coefficient.
The answer is probably that, although this effect can happen, the overall effect on small arms bullet trajectories can be neglected.