Flag priority

Jerry H

Jerry H

Different Drummer
From time to time Benchrest shooters have debated the relative importance of flag position priority. Some believe the far flags are more important and some believe the close flags are. Of course, any flag has bitten us all more than once. This would be in the absence of geographic influences for the purpose of this discussion. In other words, if a given wind is at your first flag but the rest are limp, versus all flags are limp except the last one, which will have a greater impact on the bullets position on the target? I believe the first flag will have a greater effect.

I will attempt to resolve this tomorrow in a way that can be duplicated. To test this, I finally figured out an experiment that should be valid on an outdoor range despite non-uniform winds. I ran a preliminary test last week to see if this feasible. I took a single 20 inch box fan and placed it under the bullets path about 90 feet out so that it could create an upward push on the bullet. With the fan on, the group shifted up about a ¼ inch on a 100-yard target. I repeated this several times and the results were the same under the varying wind conditions. I have since assembled four-box fans inline, so as to greatly amplify the effects and reduce the natural wind effects on the experiment. I hope to have a definitive answer tomorrow.
 
So Jerry, (COOL idea!! I like the way you think :) )

What did you find? Reason tells me that the fan closest to the muzzle should have a much larger effect than the fan closest to the target in this experiment.....

What did you find?

Does the trajectory deflect/diverge entire?? Or in "steps" over each fan??

In thinking this over..... is the test even valid? If you bumped a bullet sideways with a fan @ 90ft does the bullet take a new path?? And can the same thing happen over the gravity/trajectory curve??

hmmmmmm

al
 
If I’m correct and I won’t pretend to be infallible, this thread has diverged into two separate but intertwined issues with Al’s post. Wind drift and gyroscopic drift.

First….wind drift and flag priority:

Jerry H,
You’re correct in that flag priority is still being debated, but it shouldn’t be….because it has been proven by both practical testing and mathematical means more times than I can count.
Let me show you an analogy I’ve stolen from Professor Art Pejsa to demonstrate:
You throw a bowling ball down an alley and a gust of wind hits it 1” after you release the ball. This gust of wind imparts a ½ ft/sec cross-alley velocity to a ball traveling at 20 ft/sec or so and according to Newton’s 1st law; it retains that velocity during the rest of the time down the alley. It takes 3 seconds to reach the pins but moves (3 seconds X ½ ft/sec) and rolls in the gutter before reaching its target. A wind gust during the last inch of travel would have virtually no effect because there is no time left over which to accumulate a displacement.
The key point here is that a Force does not impart a displacement or a velocity, but it imparts an acceleration which in a period of time accumulates a change in velocity and which in that same time accumulates a displacement change.

Alinwa,
I’m not certain if your use of the word “bump” would be entirely correct for the reasons mentioned in the key point statement above . I would think even the short duration and Force imparted on the bullet from the box fan would still cause the bullet to behave no differently than a constant wind over its entire distance of flight. A strong enough gust at 90’ could be duplicated by a much smaller, but constant wind, over the entire distance.
Since you mentioned the gravity/trajectory curve, I made the assumption you were referring to the effects caused by gyroscopic drift. If that’s correct, the movement of the bullet would be so small at 100 yds that Jerry’s test would still remain valid. If you had a rifle that shoots 0’s and fired it in a tunnel, you could probably measure it but for all practical purposes….I think it’s a non-factor.

Maybe this is all BS on my part, but I’m bored this morning and don’t care if I make an ass of myself.
 
You throw a bowling ball down an alley and a gust of wind hits it 1” after you release the ball. This gust of wind imparts a ½ ft/sec cross-alley velocity to a ball traveling at 20 ft/sec or so and according to Newton’s 1st law; it retains that velocity during the rest of the time down the alley. . . .
Click to expand...

Not a I understand ballistic theory. If there were no other force being applied to the bullet, yes, that would be right. True in outer space. But in Earth's atmosphere, there is another force being applied to the bullet constantly, namely drag.

Here is a test: put a target at 20 yards. Shoot a couple rounds to get a zero. Turn the fan on at 15 yards. Shoot again, & measure how high the strike is. Now move the target back to 100 yards & repeat, keeping the fan at 15 yards. I'll bet dollars to donuts the supposed vector isn't there.

But this is all theory. We use theory because it is an accurate predictor of what will happen. Fortunately, in benchrest, we have another way -- fire a sighter. No theory with all it's wonderful powers of prediction -- & failures to predict -- needed.
 
The perplexing thing

to me anyway is how and why, with no discernable "Wind" at all, OFTEN if the flag directly in front of one's bench simply turns the bullet's flight will be grossly affected and sometimes it makes no difference at all. The tought thing about even trying to figure this out by logc is logic will let one down all too often. All of this is so range dependent , from what I have seen over the years, Logic and science seem to be in total disagreement all too often. If we couldn't shoot sighters we would be in very deep Sneakers.
 
What I attempted to say

is before anyone can begin to figure out anything about wind drift, they first need to figure out why bullets move off course when there is no wind. All the sciencei the world won't help ya if the action of the bullets are contrary to the science. :D
 
often times

Pete Wass said:
is before anyone can begin to figure out anything about wind drift, they first need to figure out why bullets move off course when there is no wind. All the sciencei the world won't help ya if the action of the bullets are contrary to the science. :D
Click to expand...

w/ no wind there is mirage (light bending) that you do not see. What we see and call mirage is actually the temperature difference between us and the target being pushed around by the wind. That refraction is just another wind flag as far as I am concerned,,,,, as long as there is wind. that is the biggest reason I HATE dead calm
 
Well, the experiment was a failure. For some reason the bullets didn't seem to be moved by the fans. The differences between today and last week were: last week cloudless, bright, and lots of mirage. Today was heavey overcast with little mirage. No verticle shift between fans off or on. Apparently what the fans were moving was the mirage affected image. Last week I used a bag gun and this week I used a rail. Oh well, back to the drawing board!
 
Lack of wind is really lack of wind that is detectable with the instruments in use at the time. A friend who is a long time competitor in the Northwest, has special flags that he sets as auxiliaries to his regular flags when conditions are very light. The respond when nothing else does, but max out to uselessness in more ordinary winds. If you put a feather on a bathroom scale and the dial does not move, does that mean that it is weightless?
 
I don't know but does a bullet behave exactly as an arrow?
I have a hard time to understand what the spinning of a bullet does but I can figure how an arrow strives to stabilize itself in the direction of it's path and how that differs from a round ball.

/Ulrik
 
a modern bullet

Ulrik Sandgren said:
I don't know but does a bullet behave exactly as an arrow?
I have a hard time to understand what the spinning of a bullet does but I can figure how an arrow strives to stabilize itself in the direction of it's path and how that differs from a round ball.

/Ulrik
Click to expand...

is NOT a round ball. Your arrow analogy is close to the truth
 
Sorry for the missunderstanding, my meaning was that the arrow could be used as a model for the bullet when comparing against the path for a round ball.
If an arrow behaves in the same way as a bullet.

/Ulrik
 
An arrow is not a good analogy. The center of pressure on an arrow in flight is well behind the center of mass -- the most pressure comes from the fletching; the mass is well forward.

A bullet is opposite; if we made bullets with the center of mass forward of the center of pressure (from the air, in flight), we wouldn't need to spin them. They would be like spears, which don't need spin to be stable.

Edit

Think on this: how about an arrow with a heavy attachment at the rear of the shaft, and the fletching at the front. It wouldn't work.
 
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As always when you think you could use a simplified way, it fails :)
I guess that the best way to understanding this is to buy the book som many refers to, written by Vaughn.
 
How about

David Halblom said:
w/ no wind there is mirage (light bending) that you do not see. What we see and call mirage is actually the temperature difference between us and the target being pushed around by the wind. That refraction is just another wind flag as far as I am concerned,,,,, as long as there is wind. that is the biggest reason I HATE dead calm
Click to expand...

when it appears to be calm and is overcast; no mirage can be seen and the first flag turns 90*? Why is it that the simple action of the flag turning causes the bullet to jump out into the 8 ring- no wind?

I did notice the other week in a match when it was calm that when a shooter several benches to my right doubled with me my bullet went 1/2 a bullet width to the left. I saw it happen and was somewhat surprised.
 
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Jerry H said:
From time to time Benchrest shooters have debated the relative importance of flag position priority. Some believe the far flags are more important and some believe the close flags are. Of course, any flag has bitten us all more than once. This would be in the absence of geographic influences for the purpose of this discussion. In other words, if a given wind is at your first flag but the rest are limp, versus all flags are limp except the last one, which will have a greater impact on the bullets position on the target? I believe the first flag will have a greater effect.

I will attempt to resolve this tomorrow in a way that can be duplicated. To test this, I finally figured out an experiment that should be valid on an outdoor range despite non-uniform winds. I ran a preliminary test last week to see if this feasible. I took a single 20 inch box fan and placed it under the bullets path about 90 feet out so that it could create an upward push on the bullet. With the fan on, the group shifted up about a ¼ inch on a 100-yard target. I repeated this several times and the results were the same under the varying wind conditions. I have since assembled four-box fans inline, so as to greatly amplify the effects and reduce the natural wind effects on the experiment. I hope to have a definitive answer tomorrow.
Click to expand...

My wind experience is with rimfire at 50 yards and I believe I am qualified to discuss this with you, Jerry. Wind on any part of the course will effect the flight of the bullet. The first part is the most critical. Sir Newton addressed in his laws of motion. "A body in motion will remain in motion until acted upon by an external force." In other words, if the bullet is pushed to the left by wind in the first few yards of flight and there are no other winds acting on it for the rest of the flight, it will continue in that direction until it reaches the target.

Does that make any sense to you?

Concho Bill
 
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Pete Wass said:
Why is it that the simple action of the flag turning causes the bullet to jump out into the 8 ring- no wind?
Click to expand...

Pete you keep saying this...... "no wind"......


THERE WAS WIND MY FRIEND!!! :) Something moved that darn flag! Seriously though, it IS air mass movement. Maybe the whole air mass between you and the target is just moving a leisurely 1mph that you can't even feel BUT IT'S MOVING!

I live on a range, have for 18yrs. There are some days (evenings) where the "wishes" (dandelion fluff) are just walking by, sometimes they'll stop and go back the other way.... BUT THE AIR NEVER STOPS..... it's pouring from one area to another all the time.

"dead calm" sucks.

AND blows! :D

AND sucks again........

LOL

al
 
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