Wind Drift: Light & Fast vs. Heavy & slow?

ryalred · December 22, 2008, 02:21 PM

I thought I knew the answer to this question but after reading a thread about shooting a .22LR at 100 yds, I'm not sure now. Which experiences the least wind drift--a light, fast bullet; or a heavy, slow bullet?

Example: Which would have the greater wind drift at 200 yds--a 30-06 shooting a 180 grain bullet or the 30-06 shooting a 150 grain bullet?

I was under the assumption that the 150 grain bullet would have more wind drift than the 180 grain bullet.

j.chappell · December 22, 2008, 02:39 PM

If the bullets are of the same design the 180gr bullet will have less wind drift than the 150gr bullet even when launched at lower velocities.

J.

DoctorXring · December 22, 2008, 03:23 PM

.

On the 30-06 rounds, it has nothing to do with bullet weight, as such.
It depends on the bullets B.C. or ballistic coefficent. A round nose
180 can have lower B.C. than a spitzer 150 and the 150 would therefore
have less wind drift. added -- this is at equal launch velocity.

On the 22 LR scenario, the slower bullet improved the accuracy on the distant
target because the bullet did not have to transition the sound barrier. When
a bullet that has been going super sonic falls below the sound barrier in speed,
destabilization occurs. You either want to stay above the speed of sound for
the whole trip, or below it for the whole trip, to the target.

dxr

T.A.Sharps · December 22, 2008, 03:26 PM

It has to do with a lot of factors, but two are bullet weight and time in the air (velocity). The longer a bullet is in the air the more time the wind has to deflect it.

If a 500gr bullet and a 50gr bullet are in the air for the same time the 50gr one will be deflected more.

If you have a 500gr bullet moving 1000fps and a 50 grain bullet moving 3000fps the slower one will be deflected more.

Surface area of the bullet too I think is a factor, such as the design of the bullet, but I have not read up on it for a while.

Are you trying to decide between different cartridges?

Brian Pfleuger · December 22, 2008, 03:29 PM

My experience is that in all cases the actual wind drift, especially at shorter ranges, is no where near what the ballistics calculators will tell you to expect.

That said, a calculator says that a 40 v-max .204 ruger bullet, mv 3900fps, will drift 13.6 inches at 200 yards in a 40mph crosswind. A 385gr Remington Core-Lokt Ultra 12ga slug at 1900 fps will drift 36.4 inches in that same wind.

Now, in all fairness, that's not a fair comarison because the cross section of the slug is HUGE compared to the v-max. The difference in same caliber bullets is much smaller.

110gr round nose 308 at 3000fps 38.7 inches, 220gr round nose at 2000fps, 31 inches

Webleymkv · December 22, 2008, 05:17 PM

Another factor is momentum (mass times velocity). All else held equal, the bullet with more momentum will be less affected by wind drift.

Demaiter · December 22, 2008, 05:32 PM

I have been mistaken - I was thinking wind deflection was the same as drop - guess its good to learn a few things every now and then

kraigwy · December 22, 2008, 06:18 PM

First off before you worry too much about Bal. tables determining wind and its affect on your bullet, you have to determine the speed of the wind. Not just where you are but anywhere between you and your target, BECAUSE IT AINT GONNA BE THE SAME. Differant People read differant wind values. I'll post a deflection fomular, but its based on you knowing exactly what the wind is doing.

D = W(T-T1)

D is the deflection
W is wind in FPS (1mph = 1.4667 fps)
T is the time of flight
T1 is the time in flight if the bullet were fired in a vacuum

With the above fomula, they make all the wind charts you see in charts found in as it takes in weight, ojive etc etc. You find the time of flight in your bal. cal. programs.

As the original poster stated, the wind chart in his Bal cal didnt match reality. That goes back my statement no one reads the wind the same way. Every ones eyes are differant, and every range is differant making conditions look differant.

The first day of sniper school in Benning, the instructors popped smoke on each yard line from 300 to 900 meters. It looked calm but the smoke went every which way. If that happens you can't tell the wind speed with any accuracy at all. So you USE mirage. Mirage seems to average out the wind giving you a pretty good ideal whats happening down range. After about 15 miles per hour or so, the wind pretty much gets constant (not always) and you can use range flags or other wind indicators.

To see what I mean about differant folks read wind differant, go to a big range during a team match and listen to the coaches call out wind corrections. You're gonna get several differant calls, but if you scope the targets, you'll see most get the same results.

There is one way, and one way only to learn wind in shooting, that is spending hours upon hours burning your eyes through a spotting scope during matches. What the NG MTU does in their Coaches Clinics is to put the coach with shooters on the All Guard team. And these are shooters, you know if the shot is off its because you called the wind wrong. That was a good start but it still takes lots of hours behind a scope to get it down. And then when coaching it depends on the shooters. Too many shooters try to second guess the coach. When that happens you have no ideal what you are doing, you can be right on on your calls but you'll never know. Military Teams are differant, you have control of the shooters and can take action if they disregard your guidence. Not so with civilian shooters.

If you're alone, and have to do it on your own, take a score or data book, check the spotting scope, make your call, make the shot and see what happens. You'll learn over time, but remember be honest with your calls. Always call and record your shots before you see the results. The Score/Data book is one of the best tools a shooter can have. USE IT

j.chappell · December 22, 2008, 06:27 PM

Quote:

Each caliber's lighter bullets will have less drift at a "closer ranges" and when you get to longer ranges the slower/heavier/higher BC bullet will have less drift.

This is not true. The heavier bullet with the higher BC has less drift from the muzzle out in all but the most extreme cases; when the lighter bullet betters the heavier by more than 400-500fps in the case of say the 22-250.

J.

B.L.E. · December 22, 2008, 10:07 PM

I think kraigwy is spot on. I have a lot of sailboat racing experience and have seen just how bad most people are at judging wind speed. Most everyone overestimates it. People will say "it's blowing 15-20" and I get out a wind meter and it says 10-12.

To better understand wind drift, consider what the bullet feels when it travels to the target. Get on a motorcycle and ride 100 mph and what do you feel? 100 mph wind coming straight back at you is what you feel. If there is a cross wind while you are riding, it only slightly changes the angle that the 100 mph wind hits you.

Likewise, a bullet going 2000 fps experiences a 2000 fps headwind and that headwind moves the bullet backward making it reach the target a few hundred feet later than it would if there was no air to travel through. A crosswind changes the angle that that 2000 fps headwind hits that bullet by a fraction of a degree and instead of blowing the bullet straight back, it also blows it off course a little.

Now it should make sense that the less velocity the bullet loses on its way to the target, the less the crosswind will deflect the bullet.

Some people seem to find it hard to accept that a subsonic .22lr drifts less than a high velocity bullet does. It's a lot easier to understand when you look at velocity decay of a bullet with a BC similar to a .22lr bullet.

These numbers are from the Lyman Black Powder manual and are for a minnie with a BC of .151.

Muzzle......1600
25 yd........1496
50 yd........1399
75 yd........1311
100 yd.......1232
125 yd......1163 (subsonic)
150 yd.......1106
175 yd.......1054
200 yd.......1010

Notice how much less the bullet sheds velocity once it goes sub-sonic.

bigalshootmupper · December 23, 2008, 12:27 AM

Yes, there are a lot of factors to consider. One factor that previous threads have come close to explaining is the factor of the velocity difference from muzzle to target. DoctorXring has it right. The more bullet velocity change from muzzle to target, the more the wind has an effect. This is not the only factor but is defintely one of them. An example is the .22LR that stays under supersonic. It will have less velocity change from muzzle to say 100yards than a supersonic and will drift less. This has been proven, but many will say it is not true. But a high velocity round, say 3500fps, will most of the time in real world shooting have less drift than lower velocity rounds because it is in the air for a shorter amount of time. It is above supersonic and is stable and therefore will not slow down as quick as a bullet that is slowing to subsonic. Ballistic coefficient is probably the most important and btw the ballistic coefficient is directly proportional to mass as BC = mass / (drag coefficent x cross sectional area).

December 22, 2008, 02:21 PM	#1
ryalred Senior Member Join Date: March 24, 2008 Location: SE Oklahoma Posts: 491	Wind Drift: Light & Fast vs. Heavy & slow? I thought I knew the answer to this question but after reading a thread about shooting a .22LR at 100 yds, I'm not sure now. Which experiences the least wind drift--a light, fast bullet; or a heavy, slow bullet? Example: Which would have the greater wind drift at 200 yds--a 30-06 shooting a 180 grain bullet or the 30-06 shooting a 150 grain bullet? I was under the assumption that the 150 grain bullet would have more wind drift than the 180 grain bullet.

December 22, 2008, 03:23 PM	#3
DoctorXring Senior Member Join Date: May 1, 2002 Location: The Republic of Texas Posts: 392	Ballistic Coefficient . On the 30-06 rounds, it has nothing to do with bullet weight, as such. It depends on the bullets B.C. or ballistic coefficent. A round nose 180 can have lower B.C. than a spitzer 150 and the 150 would therefore have less wind drift. added -- this is at equal launch velocity. On the 22 LR scenario, the slower bullet improved the accuracy on the distant target because the bullet did not have to transition the sound barrier. When a bullet that has been going super sonic falls below the sound barrier in speed, destabilization occurs. You either want to stay above the speed of sound for the whole trip, or below it for the whole trip, to the target. dxr Last edited by DoctorXring; December 22, 2008 at 03:48 PM.

December 22, 2008, 03:29 PM	#5
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,694	My experience is that in all cases the actual wind drift, especially at shorter ranges, is no where near what the ballistics calculators will tell you to expect. That said, a calculator says that a 40 v-max .204 ruger bullet, mv 3900fps, will drift 13.6 inches at 200 yards in a 40mph crosswind. A 385gr Remington Core-Lokt Ultra 12ga slug at 1900 fps will drift 36.4 inches in that same wind. Now, in all fairness, that's not a fair comarison because the cross section of the slug is HUGE compared to the v-max. The difference in same caliber bullets is much smaller. 110gr round nose 308 at 3000fps 38.7 inches, 220gr round nose at 2000fps, 31 inches __________________ https://ecommercearms.com I am the owner/operator! Ask me for custom prices! No sales tax outside CO! Last edited by Brian Pfleuger; December 22, 2008 at 03:36 PM.

December 22, 2008, 05:32 PM	#7
Demaiter Senior Member Join Date: October 27, 2008 Posts: 242	I have been mistaken - I was thinking wind deflection was the same as drop - guess its good to learn a few things every now and then Last edited by Demaiter; December 22, 2008 at 08:31 PM.

December 22, 2008, 02:39 PM	#2
j.chappell Senior Member Join Date: October 14, 2008 Posts: 1,125	If the bullets are of the same design the 180gr bullet will have less wind drift than the 150gr bullet even when launched at lower velocities. J.

December 22, 2008, 03:26 PM	#4
T.A.Sharps Senior Member Join Date: December 28, 2007 Posts: 675	It has to do with a lot of factors, but two are bullet weight and time in the air (velocity). The longer a bullet is in the air the more time the wind has to deflect it. If a 500gr bullet and a 50gr bullet are in the air for the same time the 50gr one will be deflected more. If you have a 500gr bullet moving 1000fps and a 50 grain bullet moving 3000fps the slower one will be deflected more. Surface area of the bullet too I think is a factor, such as the design of the bullet, but I have not read up on it for a while. Are you trying to decide between different cartridges?

December 22, 2008, 05:17 PM	#6
Webleymkv Senior Member Join Date: July 20, 2005 Location: Indiana Posts: 10,610	Another factor is momentum (mass times velocity). All else held equal, the bullet with more momentum will be less affected by wind drift.

December 22, 2008, 06:18 PM	#8
kraigwy Senior Member Join Date: June 16, 2008 Location: Wyoming Posts: 11,060	First off before you worry too much about Bal. tables determining wind and its affect on your bullet, you have to determine the speed of the wind. Not just where you are but anywhere between you and your target, BECAUSE IT AINT GONNA BE THE SAME. Differant People read differant wind values. I'll post a deflection fomular, but its based on you knowing exactly what the wind is doing. D = W(T-T1) D is the deflection W is wind in FPS (1mph = 1.4667 fps) T is the time of flight T1 is the time in flight if the bullet were fired in a vacuum With the above fomula, they make all the wind charts you see in charts found in as it takes in weight, ojive etc etc. You find the time of flight in your bal. cal. programs. As the original poster stated, the wind chart in his Bal cal didnt match reality. That goes back my statement no one reads the wind the same way. Every ones eyes are differant, and every range is differant making conditions look differant. The first day of sniper school in Benning, the instructors popped smoke on each yard line from 300 to 900 meters. It looked calm but the smoke went every which way. If that happens you can't tell the wind speed with any accuracy at all. So you USE mirage. Mirage seems to average out the wind giving you a pretty good ideal whats happening down range. After about 15 miles per hour or so, the wind pretty much gets constant (not always) and you can use range flags or other wind indicators. To see what I mean about differant folks read wind differant, go to a big range during a team match and listen to the coaches call out wind corrections. You're gonna get several differant calls, but if you scope the targets, you'll see most get the same results. There is one way, and one way only to learn wind in shooting, that is spending hours upon hours burning your eyes through a spotting scope during matches. What the NG MTU does in their Coaches Clinics is to put the coach with shooters on the All Guard team. And these are shooters, you know if the shot is off its because you called the wind wrong. That was a good start but it still takes lots of hours behind a scope to get it down. And then when coaching it depends on the shooters. Too many shooters try to second guess the coach. When that happens you have no ideal what you are doing, you can be right on on your calls but you'll never know. Military Teams are differant, you have control of the shooters and can take action if they disregard your guidence. Not so with civilian shooters. If you're alone, and have to do it on your own, take a score or data book, check the spotting scope, make your call, make the shot and see what happens. You'll learn over time, but remember be honest with your calls. Always call and record your shots before you see the results. The Score/Data book is one of the best tools a shooter can have. USE IT

December 22, 2008, 10:07 PM	#10
B.L.E. Senior Member Join Date: December 20, 2008 Location: Somewhere on the Southern shore of Lake Travis, TX Posts: 2,603	I think kraigwy is spot on. I have a lot of sailboat racing experience and have seen just how bad most people are at judging wind speed. Most everyone overestimates it. People will say "it's blowing 15-20" and I get out a wind meter and it says 10-12. To better understand wind drift, consider what the bullet feels when it travels to the target. Get on a motorcycle and ride 100 mph and what do you feel? 100 mph wind coming straight back at you is what you feel. If there is a cross wind while you are riding, it only slightly changes the angle that the 100 mph wind hits you. Likewise, a bullet going 2000 fps experiences a 2000 fps headwind and that headwind moves the bullet backward making it reach the target a few hundred feet later than it would if there was no air to travel through. A crosswind changes the angle that that 2000 fps headwind hits that bullet by a fraction of a degree and instead of blowing the bullet straight back, it also blows it off course a little. Now it should make sense that the less velocity the bullet loses on its way to the target, the less the crosswind will deflect the bullet. Some people seem to find it hard to accept that a subsonic .22lr drifts less than a high velocity bullet does. It's a lot easier to understand when you look at velocity decay of a bullet with a BC similar to a .22lr bullet. These numbers are from the Lyman Black Powder manual and are for a minnie with a BC of .151. Muzzle......1600 25 yd........1496 50 yd........1399 75 yd........1311 100 yd.......1232 125 yd......1163 (subsonic) 150 yd.......1106 175 yd.......1054 200 yd.......1010 Notice how much less the bullet sheds velocity once it goes sub-sonic.

December 23, 2008, 12:27 AM	#11
bigalshootmupper Senior Member Join Date: November 21, 2008 Location: Georgia Posts: 175	Yes, there are a lot of factors to consider. One factor that previous threads have come close to explaining is the factor of the velocity difference from muzzle to target. DoctorXring has it right. The more bullet velocity change from muzzle to target, the more the wind has an effect. This is not the only factor but is defintely one of them. An example is the .22LR that stays under supersonic. It will have less velocity change from muzzle to say 100yards than a supersonic and will drift less. This has been proven, but many will say it is not true. But a high velocity round, say 3500fps, will most of the time in real world shooting have less drift than lower velocity rounds because it is in the air for a shorter amount of time. It is above supersonic and is stable and therefore will not slow down as quick as a bullet that is slowing to subsonic. Ballistic coefficient is probably the most important and btw the ballistic coefficient is directly proportional to mass as BC = mass / (drag coefficent x cross sectional area).