M
model14
Guest
I think the answer to Richards Hypothesis is constant airspeed, not ground speed.....the projectile's ground speed will show a decrease while negotiating the crosswind.
And a subsonic bullet will drift less than a supersonic bullet. All things being equal.
al
Al,
The GPS and autothrottle are maintaining constant ground speed, the air speed will vary with the wind. This constraint (constant groundspeed) is a key part of the hypothesis. Stabilization (and the attendant torqueing forces)must be referenced to the ground, because these forces are the same in a vacuum (a projectile in outer space needs spin to stabilize since there are not any drag forces to keep it going straight). Now we have opened up a whole new discussion concerning the effects of density altitude (a change in air density due to temperature and barometric pressure) on a 1000 yard bullet flight.
I don't want to go there until my hypothesis is correct and understood.Richard
Gene Beggs
Active member
Richard, I will remain silent, take my seat, and turn the floor over to my new found friend and hero, Lisa Spendlove.
Lisa obviously has a deep understanding of what we have been discussing and can bring fresh, new input to the conversation.As you might expect, I didn't sleep much last night so if I run off the road on the way to Albuquerque today you will understand why.
I am thrilled to be proven wrong on this one point because I now know the truth and will be forever grateful to Lisa Spendlove and also to Alinwa and others who have disagreed with me. Al, you were right; I was wrong.
So does this new revelation invalidate everything I have ever said about wind drift? No, certainly not; all it does is clear up a minor misconception, but I will have some editing to do when I get home next week. I will have to carefully review every post I have made on this subject and make corrections as necessary.
Have a good weekend. By the way, does anyone have a good recipe for crow?
Gene Beggs
Vibe
22 Epperson Cricket
F=MABack to the OP.
model14, your initial assumption is wrong. The bullet IS NOT accelerated across the flight path by the force of the crosswind.
If there is force then there has to have been acceleration. Especially if it results in a change in a velocity vector - in either magnitude or direction.
Shoot a bullet 100 yards through a crosswind and drop a bullet 100 yards through a cross wind...see which one drifts more...if any.Likewise if you SHOOT a bullet through a crosswind and DROP a bullet through the same crosswind they should move over the same. Right??
Wrong!
First you say no acceleration..now it's different.
Force is force..both involve acceleration..the analogy is valid. The wind IS indeed the source of the force moving the bullet sideways, just as gravity is the source moving the bullet downwards. The only difference is that gravity is not imparting a drag component.
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Boyd Allen
Active member
One little point...
A fired bullet starts out at maximum velocity and drag, and they both decrease throughout its flight. A dropped bullet is just the opposite, starting out at zero, for both. As to whether velocity is required for a bullet to be moved, have you ever tried to use a plumb bob on a windy day?
A fired bullet starts out at maximum velocity and drag, and they both decrease throughout its flight. A dropped bullet is just the opposite, starting out at zero, for both. As to whether velocity is required for a bullet to be moved, have you ever tried to use a plumb bob on a windy day?
T
Tony Shankle
Guest
Vibe,
I don't know you but wanted to say that I am damn glad you joined this thread. Thank you.
Just because I am curious, do you shoot long or short range?
Tony
B
B. Harvey
Guest
Use 2 ping pong balls and fill one with whatever to increase it's weight. String them up and see which one blows more.
With the same cross section, a 25% increase in weight makes a BIG difference.
With the same cross section, a 25% increase in weight makes a BIG difference.
T
Tony Shankle
Guest
Hey...... I don't even KNOW this guy!!! He just flagged me over and asked "can you catch that plane?"
And I said yup
Next thang I know he's hangin' off a strut with an oversized JATO in one hand and duck tape in the other yelling "can you invert this thing? I can't reach!!"
So's I'm jackin' the collective and slappin' my tail trying to gain more roll (don't NEED a seatbelt since't I'm clenched like a limpet....) and this dude sez "HEY, can you draft in his propwash to null this thing outabit??? You're shakin me all up!!"
null out?? c'MON man! I'm yawed up like a funky monkin' a football, leadin' with my heels.......I mean all's I can see is ground....... I'm following that liddle skylane by keeping the hairs on the back of my neck centered up.....both feet on the panel.....
jeepers
So's I reaches out and snags that ducktape and deftly WRAPS it around his head......STOPPED HIS MUZZLE!
then that booster fired
!!
And that's all I remember.
"rigidity in space" my achin' @$%^!! I still walk like a rooster..... but at least now I know the guys name and program...!
WhaTiF Airlines all right.... at least WARN a guy! I got cawffee all over the keyboard!!
steenkin' shankle
sheeesh
al
Al, you make all this fun! Thank you!
Maybe now we can get off of airplanes and start comparing bullets to something more reasonable like knitting.
T
Tony Shankle
Guest
For you Boyd
Here you go Boyd, click on the link and on the far right side you can download a pdf of the entire book for free or you can just view online.
http://books.google.com/books?id=QdQqAAAAYAAJ&dq=Franklin+Weston+Mann&printsec=frontcover&source=bl&ots=ktiIaUe-jw&sig=I53Ns3bqKPNZiYey63o6i6TBuyU&hl=en&ei=IJnYSsaPK4Ll8Qaou6S3BQ&sa=X&oi=book_result&ct=result&resnum=3&ved=0CBMQ6AEwAg#v=onepage&q=&f=false
Here you go Boyd, click on the link and on the far right side you can download a pdf of the entire book for free or you can just view online.
http://books.google.com/books?id=QdQqAAAAYAAJ&dq=Franklin+Weston+Mann&printsec=frontcover&source=bl&ots=ktiIaUe-jw&sig=I53Ns3bqKPNZiYey63o6i6TBuyU&hl=en&ei=IJnYSsaPK4Ll8Qaou6S3BQ&sa=X&oi=book_result&ct=result&resnum=3&ved=0CBMQ6AEwAg#v=onepage&q=&f=false
Boyd Allen
Active member
Outstanding!
Big Gunner
New member
Gene,
Sorry to disappoint you, but no, I am not a pilot. I am merely a student of the rifle. I am fortunate to have a husband that is an experienced long-range competitive shooter, former marine shooting instructor, and also a student of the rifle.
Along with that, my husband and I are privileged to travel in a circle that includes a single in-law with post-graduate degrees in chemistry, physics, and mathematics; a fixed-wing Naval Aviator (Marine F/A-18’s), with a degree in aeronautical engineering; a rotary-wing Naval Aviator (Marine CH-46’s) with a degree in mechanical engineering; and a retired US Navy Master Chief that was at one time the NCOIC of the Great Lakes Naval Gunfire School (back when the “fire control computer” was a slide rule, a wind sock, and an abacus) that spent the better part of 35 years as a gunner on destroyers.
When a discussion of “how a bullet flies” comes up around these guys you’d better hang on and have the rest of the afternoon available.
When I first showed an interest in rifle shooting, my husband (who is a wonderful teacher) made it plain that he would teach me everything he knew, and lots of things he thought about the accurate rifle and the precision shot. That was the catch. I HAD TO LEARN about shooting. Not just go to the range and yank the trigger.
He taught me what he knew about internal ballistics, and we researched more, going over new or different ideas as they were presented so that I had a thourough understanding of the mechanics of initiating the shot to preceed my introduction to reloading.
We debated contrasting sides of all of the aspects of exterior ballistics, studying the views and opinions of all the different “experts”. In many cases, we experiment (as best we can) with the varying concepts that are floating around out there. We keep what works and reject the rest.
I have spent countless hours discussing things like wind “deflection” (whatever that really is), sectional density, ballistic coefficient, and what happens if you fire a bullet in the absence of gravity—more on that in a minute—at the dinner table and at fine restaurants all over the country in the company of some (if not all) of the people mentioned above.
Like I said: if you want a “lively discussion” on how a bullet flies, get a physicist, an aeronautical engineer, a naval gunfire expert, and marine rifle team member together at the same table. Just hold on and order more than one cocktail.
Some of that is bound to rub off. Even a blind pig will find some truffles.
Caution—At this point I am oversimplifying—Caution
Mostly, what I believe on the issue of bullet flight is this: Everyone gets caught up in the “what would happen in a vacuum” vs. “what happens in the atmosphere” debate.
I think most of the discussion would become easier to understand if we debated “WHAT WOULD HAPPEN IN THE ABSENCE OF GRAVITY”. With the absence of gravity, but not in a vacuum, all of the forces that affect the bullet are present; the bullet just never falls to the ground.
What happens if a bullet is fired in the absence of gravity? If it is fired on a level plane, it will continue to travel dead ahead (wind, the coriolis, magnus, and other forces excluded for the moment) until its forward momentum stops. If nothing else acts on the bullet except the drag created by coasting through the atmosphere, the bullet will continue to travel unimpeded and continue to bleed velocity until it comes to a dead stop, where is will just hang there as the earth rotates out from under it.
Likewise, it will ALWAYS bleed velocity directly opposite the drag (I know, it is really in the direction of drag, but it is easier to think of it as opposite).
If we impart a 90 degree crosswind on this bullet (in the absence of gravity) as it is flying along, it will precess (pointing its nose into the crosswind) and, as it bleeds velocity directly opposite its drag, it will slow down in the opposite direction of its nose. This is what most people refer to a “wind drift”. As the bullets’ velocity approaches the velocity of the crosswind the bullet will precess further and further into the wind. When the forward velocity is the same as the crosswind, the bullet will precess at a 45 degree angle to both the wind and original direction of travel. When the forward velocity decreases to zero, and if the crosswind is still blowing, the bullet will precess directly into the crosswind (or be completely sideways to the bore). Eventually, the wind would start pushing the bullet backwards. In other words, pushing the bullet ass backwards accelerating the bullet until it reached a speed equal to the wind velocity.
This is why, if a bullet is fired from one balloon moving in an air mass, at a target fixed to another balloon traveling in the same air mass, the bullet will still exhibit “wind drift”. It is this precession, and the corresponding velocity loss in the opposite direction of drag that causes the bullet to “drift”.
This is why a fired bullet and a bullet dropped from sufficient height to achieve terminal velocity do not exhibit the same amount of “wind drift”.
Anyway, that’s what I think.
Lisa
Sorry to disappoint you, but no, I am not a pilot. I am merely a student of the rifle. I am fortunate to have a husband that is an experienced long-range competitive shooter, former marine shooting instructor, and also a student of the rifle.
Along with that, my husband and I are privileged to travel in a circle that includes a single in-law with post-graduate degrees in chemistry, physics, and mathematics; a fixed-wing Naval Aviator (Marine F/A-18’s), with a degree in aeronautical engineering; a rotary-wing Naval Aviator (Marine CH-46’s) with a degree in mechanical engineering; and a retired US Navy Master Chief that was at one time the NCOIC of the Great Lakes Naval Gunfire School (back when the “fire control computer” was a slide rule, a wind sock, and an abacus) that spent the better part of 35 years as a gunner on destroyers.
When a discussion of “how a bullet flies” comes up around these guys you’d better hang on and have the rest of the afternoon available.
When I first showed an interest in rifle shooting, my husband (who is a wonderful teacher) made it plain that he would teach me everything he knew, and lots of things he thought about the accurate rifle and the precision shot. That was the catch. I HAD TO LEARN about shooting. Not just go to the range and yank the trigger.
He taught me what he knew about internal ballistics, and we researched more, going over new or different ideas as they were presented so that I had a thourough understanding of the mechanics of initiating the shot to preceed my introduction to reloading.
We debated contrasting sides of all of the aspects of exterior ballistics, studying the views and opinions of all the different “experts”. In many cases, we experiment (as best we can) with the varying concepts that are floating around out there. We keep what works and reject the rest.
I have spent countless hours discussing things like wind “deflection” (whatever that really is), sectional density, ballistic coefficient, and what happens if you fire a bullet in the absence of gravity—more on that in a minute—at the dinner table and at fine restaurants all over the country in the company of some (if not all) of the people mentioned above.
Like I said: if you want a “lively discussion” on how a bullet flies, get a physicist, an aeronautical engineer, a naval gunfire expert, and marine rifle team member together at the same table. Just hold on and order more than one cocktail.
Some of that is bound to rub off. Even a blind pig will find some truffles.
Caution—At this point I am oversimplifying—Caution
Mostly, what I believe on the issue of bullet flight is this: Everyone gets caught up in the “what would happen in a vacuum” vs. “what happens in the atmosphere” debate.
I think most of the discussion would become easier to understand if we debated “WHAT WOULD HAPPEN IN THE ABSENCE OF GRAVITY”. With the absence of gravity, but not in a vacuum, all of the forces that affect the bullet are present; the bullet just never falls to the ground.
What happens if a bullet is fired in the absence of gravity? If it is fired on a level plane, it will continue to travel dead ahead (wind, the coriolis, magnus, and other forces excluded for the moment) until its forward momentum stops. If nothing else acts on the bullet except the drag created by coasting through the atmosphere, the bullet will continue to travel unimpeded and continue to bleed velocity until it comes to a dead stop, where is will just hang there as the earth rotates out from under it.
Likewise, it will ALWAYS bleed velocity directly opposite the drag (I know, it is really in the direction of drag, but it is easier to think of it as opposite).
If we impart a 90 degree crosswind on this bullet (in the absence of gravity) as it is flying along, it will precess (pointing its nose into the crosswind) and, as it bleeds velocity directly opposite its drag, it will slow down in the opposite direction of its nose. This is what most people refer to a “wind drift”. As the bullets’ velocity approaches the velocity of the crosswind the bullet will precess further and further into the wind. When the forward velocity is the same as the crosswind, the bullet will precess at a 45 degree angle to both the wind and original direction of travel. When the forward velocity decreases to zero, and if the crosswind is still blowing, the bullet will precess directly into the crosswind (or be completely sideways to the bore). Eventually, the wind would start pushing the bullet backwards. In other words, pushing the bullet ass backwards accelerating the bullet until it reached a speed equal to the wind velocity.
This is why, if a bullet is fired from one balloon moving in an air mass, at a target fixed to another balloon traveling in the same air mass, the bullet will still exhibit “wind drift”. It is this precession, and the corresponding velocity loss in the opposite direction of drag that causes the bullet to “drift”.
This is why a fired bullet and a bullet dropped from sufficient height to achieve terminal velocity do not exhibit the same amount of “wind drift”.
Anyway, that’s what I think.
Lisa
Vibe
22 Epperson Cricket
Very well stated.
The same effect would take place in your wind driven exercise before the bullet reached the 45° precession point.
Other than that, it's a nice analogy.
noted - and appreciated.
I have to call into question the conclusion of this thought exercise. as the bullet would not reach the 90° to bore position. Once the overturning moment became less than what the gyroscopic stability could resist - the bullet would stop precessing into the wind and just accept (or ignore) the side load. Rotational speed is lost much slower than lateral velocity - which makes bullets continuously gain in stability. At some point, and for most of us it is outside of the range of use for our projectiles, the bullet gains enough in the stability vs overturning moment that the bullet will no longer "nose over" into the growing upward wind direction (due to falling). This is most often seen in the too light (for caliber) for the job bullets fired at too steep of an angle at too long a range. They reach the point where the force at the Center of Pressure is just not enough to really influence the growing relative stability - resulting in bullet flying through the target nose high, or in some other attitude if coning has set in.
The same effect would take place in your wind driven exercise before the bullet reached the 45° precession point.
Other than that, it's a nice analogy.
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Big Gunner
New member
Vibe,
Thank you, and I agree with your assesment of my conclusion.
I was just trying to explain in a manner in which everyone could visualize what I was saying. At some point, the bullet WILL stop turning into the wind and simply act as any other object in the air mass.
Often-times in these discussions a concept is difficult to visualize, so I tend to break it down to simple (if not exactly accurate), easy to explain concepts. Once the basic concept is visualized, those of us that aren't engineers, or mathematicians, can move onto the more advanced stuff that takes the minutiea into account.
Lisa
Thank you, and I agree with your assesment of my conclusion.
I was just trying to explain in a manner in which everyone could visualize what I was saying. At some point, the bullet WILL stop turning into the wind and simply act as any other object in the air mass.
Often-times in these discussions a concept is difficult to visualize, so I tend to break it down to simple (if not exactly accurate), easy to explain concepts. Once the basic concept is visualized, those of us that aren't engineers, or mathematicians, can move onto the more advanced stuff that takes the minutiea into account.
Lisa
Boyd Allen
Active member
Al,
What Mann did was to drop bullets from the same height as their drops would be when fired from horizontal barrel at targets at 100 and 200 yards. The drop distances were 9 7/8" and 41" respectively. He measured their wind drifts. The drift for the shorter drop was .08" and for the longer .30, the latter from a wind speed of 24 mph. He then computed how far the bullet would have drifted if it had moved at the same speed as the wind for the same amount of time that it took it to drop.That is where the 620 to 1 ratio come from, NOT comparison of the dropped drift and the actual drift of a fired bullet. Based on previous posts, I thought that this needed clearing up.
What Mann did was to drop bullets from the same height as their drops would be when fired from horizontal barrel at targets at 100 and 200 yards. The drop distances were 9 7/8" and 41" respectively. He measured their wind drifts. The drift for the shorter drop was .08" and for the longer .30, the latter from a wind speed of 24 mph. He then computed how far the bullet would have drifted if it had moved at the same speed as the wind for the same amount of time that it took it to drop.That is where the 620 to 1 ratio come from, NOT comparison of the dropped drift and the actual drift of a fired bullet. Based on previous posts, I thought that this needed clearing up.
This is correct Boyd, I hadn't realized that it could be confusing
as I was only trying to use it to illustrate that "something other than the wind blowing on the bullet" was at work.So much of this stuff gets shortcut in these discussions and a lot of the confusion comes from the fact that we each live and read in our own heads.
Perty cool that the book's online...... look up the part about where he built a muslin 100yd TUNNEL! Not as cool as Beggs' tunnel but you gotta' give him an A for effort.
Thank you, nice catch
al
Boyd Allen
Active member
I guess my point about this is that his comment really had nothing to do with the real situation of bullet being moved by the wind, bullets being rather dense, and the resultant inertia, and the wind not being able to "get a hold" of a bullet to any great degree, due to its fluidity, and a bullet's, for lack of a better term, "sidewise streamlining". All of this predicts that a bullet will not take off sideways in instant synchronization with a crosswind.