Because the ole wiki knows better than the person who single-handedly created the most accurate ballistics modeling available?
I think people are talking about two separate phenomenons here.
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Because the ole wiki knows better than the person who single-handedly created the most accurate ballistics modeling available?
I think people are talking about two separate phenomenons here.
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I'm not misunderstanding Litz at all. That is physically incorrect. The formula and science doesn't change. You lose angular momentum as you lose rotational velocity. That's the end of the story.
His modeling may be super accurate, but his language isn't. He's either being obtuse with it on purpose so laymen can understand it, or misusing terminology. The gyroscopic stability won't change with anything other than a loss in rotational velocity. Get over it.
The bullet MAY be more precise as it slows down, however, but that wouldn't be due to gyroscopic stability. That would be due external factors like non-uniform jacket construction being less affected at slower velocities, etc. etc.
But all other factors don't remain equal. Quite obviously the airflow over the bullet changes dramatically as it slows. Sure, if we just spun a stationary bullet at a given RPM it would be more stable than the same bullet at a lower RPM, but Litz' point is that as the bullet travels through the atmosphere and sheds forward velocity the destabilizing effects dissipate more quickly than the stabilizing effect of the rotational speed is reduced. Again, Litz is talking about actually shooting the bullet through the air, not just spinning it with "all other factors being equal."
And like I said above, he's using the wrong terminology. Gyroscopic stability IS exactly that: a static (not stationary; static can be moving so long as the system isn't changing) thing. If you bring other factors like wind and jacket irregularities into account, you are no longer talking about gyroscopic stability.
I understand perfectly what Litz is saying. His language is incorrect. Gyroscopic stability is not increasing. It is decreasing just like everything else in the system, just at a lesser rate. This may have tangible, counter-intuitive effects of greater precision at certain ranges than others (I'm not making a claim on that, I don't know) since it is proportionally decreasing at a lesser rate than other factors, but the fact is it's still decreasing.
Oh, ok. So you feel like engaging in pedantic quibbling when it's plainly obvious to anyone with a modicum of critical thinking ability exactly what Litz is talking about. None of that changes the fact that the observed effect of the bullet becoming more stable as it sails downrange (save for transonic speeds) is entirely true and what actually matters in the real world.
A projectile will exhibit yawing, precession and nutation during flight.
Yaw and precession will decrease the further away from the barrel the projectile travels.
http://imageshack.com/a/img28/605/e6z1.gif
Here is a video describing how this actually looks:
http://www.youtube.com/watch?v=4pF8W5liSRc#t=65
So yes, a bullet is more stable in flight further down range, than it is immediately after leaving the barrel.
However, this refers to dynamic stability, not static/gyroscopic stability. Dynamic stability is what the diagram above shows, static/gyroscopic stability refers to sufficient/insufficient spin.
It's not quibbling. Someone said gyroscopic stability increases as the bullet slows down, and it doesn't. It objectively decreases. That's really the end of the story. Our language matters in circumstances of science and technical discussion, because misusing these terms spreads misinformation.
Stop taking it so personally.
EDIT: see above. See? These are two COMPLETELY different phenomenon. We need to get them right if we are to have productive and accurate discussions on these topics. It's like confusing gravity and magnetism. Sure, they both suck things towards them, but they aren't the same thing. This topic just gets even more confusing because they're both a type of "stability." I didn't choose the language, but it should be accurate if we want to gain a true understanding of the mechanics of bullet stability.
Perhaps you should write Bryan Litz a letter and clear that up then since his word is essentially the Gospel as far as the field of external ballistics is concerned.
And once more, the observed effect is exactly consistent with what Litz says even if you take issue with a certain word he used.
The observed effect is consistent with dynamic stability, not gyroscopic. Language matters in applications of science.
This is especially important in a discussion of twist rate, which is a discussion of gyroscopic stability. Getting all of these terms mixed up is like confusing alpha, beta, and gamma radiation, which are also completely different phenomena. You can't use these things interchangeably.
Anyway, I've made my point. If you want to continue taking it personally, that's fine. Science prevails regardless. Hopefully those who come across this thread in the future will find themselves more educated on the subject regardless of argument, because that's important when it comes to understanding the technical aspects of firearms function.
Well, at least you got your answer to what you posted above. You were only focusing on gyroscopic stability, and ignoring the effect of dynamic stability. Perhaps Litz should have used the word "dymanic" rather than "gyroscopic" but other than that his explanation perfectly fits the observed effect and answers your disbelief that the bullet becomes more stable as it heads downrange.