05-17-2007, 08:44
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#16
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Guerrilla
Join Date: Sep 2006
Location: GA
Posts: 184
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speedy...
Coriolis effect will have about as much impact on getting your ex's Durango out of my driveway as it would on field ballistic dope.
You got punked 
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If I see one more shirttail flapping while I'm captain of this ship - woe betide the sailor; woe betide the OOD; and woe betide the morale officer. I kid you not. - Capt Queeg, The Caine Mutiny. 
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kachingchingpow is offline
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05-17-2007, 08:51
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#17
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Bladesmith to the Quiet Professionals
Join Date: Feb 2004
Location: Oregon, Land of the Silver Grey Sunsets
Posts: 3,886
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what I've learned here:
when hunting and shooting on a north-south axis the earth will rotate a tree in front of the running elk just as the trigger is squeezed.
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Bill Harsey is offline
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05-17-2007, 08:55
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#18
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Area Commander
Join Date: Feb 2005
Location: Pacific NorthWet
Posts: 1,495
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Quote:
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Originally Posted by Bill Harsey
what I've learned here:
when hunting and shooting on a north-south axis the earth will rotate a tree in front of the running elk just as the trigger is squeezed.
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Bill, thank you for explaining all of this, I was wondering if my two remaining brain cells where still functioning. Over the years I have had shots like that and never knew why. I will tape a compass to my hunting rifle barrel with a note attached, "shooing N or S is a no no". I hope I got it right. 
Hopefully, I fill my freezer with some tasty Roosevelt Elk meat this season.
Best,
H.
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HOLLiS is offline
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05-17-2007, 09:36
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#19
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Guerrilla
Join Date: Aug 2006
Location: Western WI
Posts: 176
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Quote:
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Originally Posted by HOLLiS
Bill, thank you for explaining all of this, I was wondering if my two remaining brain cells where still functioning. Over the years I have had shots like that and never knew why. I will tape a compass to my hunting rifle barrel with a note attached, "shooing N or S is a no no". I hope I got it right.
Hopefully, I fill my freezer with some tasty Roosevelt Elk meat this season.
Best,
H. |
Wait, WAIT!...
Now you've intorduced the variable of magnetism with relation to the distance of the compass from the barrel!
And just when this was making sense... : 
Last edited by Rumblyguts; 05-17-2007 at 09:51.
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Rumblyguts is offline
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05-17-2007, 09:51
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#20
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Quiet Professional
Join Date: Jan 2004
Location: Free Pineland
Posts: 24,825
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Here is an excellent scientific explanation of how bullets fly, for anyone who is interested in the technical explanation of the forces acting upon a projectile in flight:
http://www.nennstiel-ruprecht.de/bul..._forcesmoments
The actual formula for computing the Coriolis effect on a projo is here:
http://www.nennstiel-ruprecht.de/bul...olf.htm#header
Uggh, too hard, physics of ballistics make Zog's head hurt. Need Reader's Digest version.
Their summation of the effect is "The magnitude of the fictitious Coriolis force is so small that it is usually completely neglected and - as a rule of thumb - only has to be considered in ballistics for ranges of 20 km or more (artillery shells)."
TR
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"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat." - President Theodore Roosevelt, 1910
De Oppresso Liber 01/20/2025
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The Reaper is offline
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05-17-2007, 16:42
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#21
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Quiet Professional
Join Date: Sep 2005
Location: NC for now
Posts: 2,418
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A little off topic. Someone on this board showed me a simple way to explain why we read winds 2/3 the distance to the target, LongRange. He was explaining to the Students why the wind effects the Bullet at this point more then any other .
He said "with the wind blowing, throw a ball straight up in the air, notice the wind will move the ball in that split second it becomes weightless" Thats why we read winds where the Bullet reaches it's max trajectory. Bullet becomes weightless like the ball. At this point the effects of wind overtake the effects of gravity.
This is also why the wind speed at your shooting position is of little importance. Thought this was a good analogy and always used it successfully. Of course I never give him credit for this analogy
If you don't have an answer for a Student for why his groups are all over the place. Need a little time to figure it out. A good one to use is "It's possible your Barrel Harmonics are off" Big word for something might be touching your free floated Barrel. Just like (PPIM) Pre Primer Ignition Movement. Jerking the Trigger.
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Sounds like a s#*t sandwhich, but I'll fight anyone, I'm in.
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kgoerz is offline
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05-17-2007, 19:40
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#22
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Quiet Professional
Join Date: Jun 2004
Location: Occupied Pineland
Posts: 4,701
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This is fun! And nobody's mentioned "spin drift" yet.  I do remember that from the 4.2 mortar class in the heavy portion of the Weapons "Q" course. Peregrino
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Peregrino is offline
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05-17-2007, 19:53
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#23
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Quiet Professional
Join Date: Jan 2004
Location: Free Pineland
Posts: 24,825
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Quote:
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Originally Posted by Peregrino
This is fun! And nobody's mentioned "spin drift" yet. I do remember that from the 4.2 mortar class in the heavy portion of the Weapons "Q" course. Peregrino |
Actually, they have.
Quote:
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Originally Posted by JLF
It ties the GPS, Kestrel, LRF, and Ballistic PDA together and he said it will consider Coriolis and Magnus effects.
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The Magnus effect is the technical term for spin drift.
TR
__________________
"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat." - President Theodore Roosevelt, 1910
De Oppresso Liber 01/20/2025
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The Reaper is offline
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05-17-2007, 20:23
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#24
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Area Commander
Join Date: Nov 2004
Location: Lone Star
Posts: 2,153
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Tradeoff and max trajectory
Reaper Sir, thanks for the links. Those are what I've been looking for for years. My google-fu needs tons of tune-ups.
Quote:
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Originally Posted by kgoerz
...we read winds 2/3 the distance to the target.....
...wind effects the Bullet at this point more then any other...
...wind will move the ball in that split second it becomes weightless...
...we read winds where the Bullet reaches it's max trajectory...
...Bullet becomes weightless like the ball...
...At this point the effects of wind overtake the effects of gravity.
...wind speed at your shooting position is of little importance...
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ugh...nerd time! I'll be here all night. So I better share the headache. I may have to PM longrange on this when it gets too long and convoluted
1. The tradeoff puzzle. The wind affects the bullet more the further it is from the muzzle as it is losing its kinetic energy/forward momentum. On the other hand, while the effect of wind is small at muzzle, the smallest deviation caused by the wind will propagate over distance.
So the correct answer is at 2/3 the distance ??? Why?
2. Since trajectory is the path a moving object follows through space, what is max trajectory? The end of the path? The point where bullet is weightless? The ball analogy works where force of gravity = upward force (that split second 0 gravity state at max height), but then the bullet will also have to be at the max height and that is 1/2 of the distance, not 2/3 ???
I've almost given up 100% testing scientific reasonings at the range and accepted what the old salts said that lrs is more of an art than science. Indeed, paying attention to basics, being in the "zone" and hard holds give more results that xyz physics, but still...."curiosity kills the cat, but satisfaction brings it back"
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"we also rejoice in our sufferings, because we know that suffering produces perseverance; perseverance, character; and character, hope" Rom. 5:3-4
"So we can suffer, and in suffering we know who we are" David Goggins
"Aide-toi, Dieu t'aidera " Jehanne, la Pucelle
Der, der Geld verliert, verliert einiges;
Der, der einen Freund verliert, verliert viel mehr;
Der, der das Vertrauen verliert, verliert alles.
INDNJC
Last edited by frostfire; 05-17-2007 at 20:25.
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frostfire is offline
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05-17-2007, 20:27
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#25
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Quiet Professional
Join Date: Jan 2004
Location: Free Pineland
Posts: 24,825
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Quote:
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Originally Posted by frostfire
2. Since trajectory is the path a moving object follows through space, what is max trajectory?
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Max ordinate, the apogee of the bullet's path.
TR
__________________
"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat." - President Theodore Roosevelt, 1910
De Oppresso Liber 01/20/2025
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The Reaper is offline
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05-17-2007, 20:55
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#26
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Area Commander
Join Date: Nov 2004
Location: Lone Star
Posts: 2,153
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question answered
ok, after reading several ballistics for dummies, I learnt that maximum ordinate is beyond the midrange. Hence, 2/3 the distance makes perfect sense.
Should have thought of this earlier, as the bullet slows down, gravity and air friction have more effect.
I'll just have to take it that wind at 2/3 distance dominates over any propagated deviation from wind at muzzle. Now back to reading flags and setting the scope to see mirage at 2/3 range. So much for toss-grass-in-the-air method.....living and (always) learning.
__________________
"we also rejoice in our sufferings, because we know that suffering produces perseverance; perseverance, character; and character, hope" Rom. 5:3-4
"So we can suffer, and in suffering we know who we are" David Goggins
"Aide-toi, Dieu t'aidera " Jehanne, la Pucelle
Der, der Geld verliert, verliert einiges;
Der, der einen Freund verliert, verliert viel mehr;
Der, der das Vertrauen verliert, verliert alles.
INDNJC
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frostfire is offline
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05-17-2007, 21:03
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#27
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Quiet Professional
Join Date: Jan 2004
Location: Free Pineland
Posts: 24,825
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Once the bullet goes subsonic, it really gets squirrelly and prone to deflection.
TR
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"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat." - President Theodore Roosevelt, 1910
De Oppresso Liber 01/20/2025
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The Reaper is offline
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05-18-2007, 05:33
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#28
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Quiet Professional
Join Date: Jan 2004
Location: Fayetteville NC
Posts: 3,533
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Quote:
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Originally Posted by Peregrino
This is fun! And nobody's mentioned "spin drift" yet. I do remember that from the 4.2 mortar class in the heavy portion of the Weapons "Q" course. Peregrino |
Reference Reaper below your post.
You guys are starting to make my head hurt! Reaper! Dam man, that formula will kill you and the effect is just too slight to be worth computing unless you are going ballistic in sniping.
Interestingly, a subsonic bullet actually has a better BC then it did just prior to transition. Go figure!
It is squirrely as heck though.
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Hold Hard guys
Rick B.
Knowledge is knowing a tomato is a fruit.
Wisdom is knowing it is great on a hamburger but not so great sticking one up your ass.
Author - Richard.
Experience is what you get right after you need it.
Author unknown. 
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longrange1947 is offline
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05-18-2007, 07:35
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#29
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Quiet Professional
Join Date: Jan 2004
Location: Free Pineland
Posts: 24,825
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I am still trying to wrap my head around a variable BC as the bullet flies.
TR
__________________
"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat." - President Theodore Roosevelt, 1910
De Oppresso Liber 01/20/2025
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The Reaper is offline
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05-18-2007, 07:47
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#30
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Quiet Professional
Join Date: Jan 2004
Location: Fayetteville NC
Posts: 3,533
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Quote:
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I am still trying to wrap my head around a variable BC as the bullet flies.
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That is why alot of the ballistic "predictor" programs fail as they do not take into account that the BC changes with velocity. Sierra, atleast, shows three to four BCs with speed envelopes to get a basic prediciton. Presicion Workbench uses a modeled curve based on actual performance of your bullet/weapon combination at specific ranges.
As the velocity approaches trans sonic it falls off rapidly and then during subsonic shift it jumps back up. It flies really well but is very suseptable to any changes in air resistance as from wind shift to thermals. The round is spinning at a higher ratio to forward velocity so the round is now nose high and overstablized (gyroscopic) making it even more suseptable to violent tilts in axis, just as a gyroscope tilts once upset.
Predicitng bullet flight at those speeds is right next to impossible as so many things come into play.
__________________
Hold Hard guys
Rick B.
Knowledge is knowing a tomato is a fruit.
Wisdom is knowing it is great on a hamburger but not so great sticking one up your ass.
Author - Richard.
Experience is what you get right after you need it.
Author unknown.
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longrange1947 is offline
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