Range Report Spin Drift?

J

jsthntn247

Gunny Sergeant
Full Member
Minuteman
Feb 25, 2009
1,213
144
Mississippi
#1
Aight guys, I have a 2 part question for ya. Long range for me in Mississippi is 450 yards. I shot today at 725 yards. My guns are perfiectly capable of .5moa groups at 450 yards, I have shot this on numerous occasions. I have just never pushed it past that distance.

1. At 725, I was 2.25 moa to the right. The wind was directly at my back and was only about 2.5 mph. I verified my zero at 200 with a 3 shot .75" group before moving back to 725. This is with a 7rem mag shooting 162 sst at 2895. I am wondering if this has to do with spin drift???

2. I alsot shot my .257 weatherby at 725. It is a Remington SPS that I bedded into a B&C Mealist. I can't figure out what's going on with this gun. All shots are reloads. Some reloads are very hard to chamber and some are very easy. The reloads that are hard to bolt down all have a mark on the belt itself. However, when shooting at 725 I shot a 2" group with the hard to close reloads, but couldn't even hit paper with the ones that were easy to close and both were loaded the exact same and both were with twice fired brass. Also, this gun needed 1.25 moa adjustment to the right to hit center at 725. This gun is loaded with 100gr Scirrocco's at 3700 fps. Does the 1.25 moa also have to do with spin drift???
 
#2
Re: Spin Drift?

I've never seen a wind remain at no value across 725 yds. There is always something happening with it that will push your bullet in one direction or another. Were you able to use flags or observe the mirage to make a downrange wind call? What were the other shooters on the line (if there were any) calling the wind at?

There's always the shooter factor in there too, and sometimes the tiny errors don't show until you push the distance out there.

The subject of spin drift has been beaten to death, just run a search.
Google Search Spin Drift
 
#3
Re: Spin Drift?

Without beating this subject to death AGAIN, I recommend getting a copy of Bryan Litz' book "Applied Ballistics for Long Range Shooting" and read up on the subject of Gyroscopic (spin) drift, the Coriolis Effect, etc. and see what it actually does. Not because you need to adjust for it moving from 450 to 725 yards, but to show you it doesn't make that much difference. What Mr. Litz book will really do is to show you there is something else causing the errors, the shooter, and mis-judging the wind, etc. etc.

I've been shooting 1000 yard matches a long time, and as mentioned above, I have never seen a steady 2.5 mph wind constant across the course, and lenth of the shooting session. A one MPH miscalulation of wind will get you more then wind drift at the ranges you are talking about.
 
#4
Re: Spin Drift?

What happens at 500rds an in, w/a center fire, is about like a 22lr at 50-60 yds. Past that, the river of wind may or may not, be seen via objects your looking at or can even see. Wind/environment reading ability is a skill that can not be learned from reading a book, watching a movie, or staying at a Holiday Inn Express. Only after you have mastered the wind should you worry about other things, most worry about. Even then all the worry is for not, if your up on field skills.


The only way to be a player, is to get out an play, an play often. Gizmos, help but the brain or log book require no battery's. YMMV
 
#5
Re: Spin Drift?

Spin drift is a factor, but not so much at 700-800 yards. When shooting my 308 w/ 175 SMKs at 1,300 yards spin drift was a huge factor. I don't remember exact number off hand, but it was 1.5-2 MOA.
 
#7
Re: Spin Drift?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Redmanss</div><div class="ubbcode-body">I've never seen a wind remain at no value across 725 yds. There is always something happening with it that will push your bullet in one direction or another. Were you able to use flags or observe the mirage to make a downrange wind call? What were the other shooters on the line (if there were any) calling the wind at?

There's always the shooter factor in there too, and sometimes the tiny errors don't show until you push the distance out there.

</div></div>

I had no value on wind at 1000 yards two days ago despite a steady mirage left to right. High BC rounds and wind currents that occur late in the flight time can make for a long shot without much correction.

That said, its about the only time its happened to me at the range so far.

Rich
 
#9
Re: Spin Drift?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jsthntn247</div><div class="ubbcode-body">Aight guys, I have a 2 part question for ya. Long range for me in Mississippi is 450 yards. I shot today at 725 yards. My guns are perfiectly capable of .5moa groups at 450 yards, I have shot this on numerous occasions. I have just never pushed it past that distance.

1. At 725, I was 2.25 moa to the right. The wind was directly at my back and was only about 2.5 mph. I verified my zero at 200 with a 3 shot .75" group before moving back to 725. This is with a 7rem mag shooting 162 sst at 2895. I am wondering if this has to do with spin drift???

2. I alsot shot my .257 weatherby at 725. It is a Remington SPS that I bedded into a B&C Mealist. I can't figure out what's going on with this gun. All shots are reloads. Some reloads are very hard to chamber and some are very easy. The reloads that are hard to bolt down all have a mark on the belt itself. However, when shooting at 725 I shot a 2" group with the hard to close reloads, but couldn't even hit paper with the ones that were easy to close and both were loaded the exact same and both were with twice fired brass. Also, this gun needed 1.25 moa adjustment to the right to hit center at 725. This gun is loaded with 100gr Scirrocco's at 3700 fps. Does the 1.25 moa also have to do with spin drift??? </div></div>

It is only 725. SO being helpful rather than sarcastic....

1. Spin drift - no (too much 'error'). Wind - probable; Shooter - probable;

2. It may not be your rifle but you definitely have an issue with your ammunition.

All your reloads are the same? You have evidence yourself that they are not. The bolt does not close the same. You may run the same process on each round but unless you actually measure the dimensions of each round how do you know they are the same => you don't. Start there. Search the site there have been lots of questions and answers on this topic.
 
#10
Re: Spin Drift?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I vote for coriolis, I know when I throw a baseball in the air as high as I can, depending on the hang time I have to take at least a full step to the side to catch it. </div></div>

I may have to try the baseball thing because I know I can't shoot well enough for it to show on my targets.
 
#11
Re: Spin Drift?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I vote for coriolis, I know when I throw a baseball in the air as high as I can, depending on the hang time I have to take at least a full step to the side to catch it. </div></div>


laugh.gif
laugh.gif
laugh.gif
 
#12
Re: Spin Drift?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I vote for coriolis, I know when I throw a baseball in the air as high as I can, depending on the hang time I have to take at least a full step to the side to catch it. </div></div>

No way. The effect is much smaller. I think you can't throw the ball perpendicular to the earth, so it's an inclined throw.
 
#13
Re: Spin Drift?

I had wind flags all along the course and they were all blowing toward the target but barely moving. I fired a 3 shot group measuring 2.40" then moved left 2.25 moa and put 3 in dead center in a softball sized target. I have a feeling it might be in the scope turret. I put a level on the raceways, picatinny, and turret and had a level crosshair drawn on a 50 yard target. When the gun and crosshairs are level together, the level on top of the turret is turned a considerable amount. Could my vertical crosshair be missaligned cause me to be adding windage when dialing up moa??? I put the scope on by leveling the crosshairs on a 50 yard target while the gun was leveled in two places. The scope is a Viper 6-20x50.
 
#14
Re: Spin Drift?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I vote for coriolis, I know when I throw a baseball in the air as high as I can, depending on the hang time I have to take at least a full step to the side to catch it. </div></div>

It's easy to gauge the Coriolis. Drink a bottle of Jack Daniels in 10 secs.. soon you will begin to feel the Earth moving underneath you. Before you know it, you'll be hanging on the grass to stop from falling off of the Earth. I would gauge Coriolis a three days before shooting though.
 
#17
Re: Spin Drift?

Come out and shoot a few 1000 yard matches and you'll be convinced of many tings but two constants are that:

1. there is no such thing as a "no wind scenario" <--- OK, maybe someone else has used it but I'm claiming that one till proven otherwise
smile.gif


2. sometimes there is just something happening that you can't see, and it does however feel somewhat better to see that the guy next to you cant see it either. :p
 
#18
Re: Spin Drift?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: XTR</div><div class="ubbcode-body">1. there is no such thing as a "no wind scenario" <--- OK, maybe someone else has used it but I'm claiming that one till proven otherwise
smile.gif
</div></div>

Just to clarify my own post, there is a difference between no wind, and no value. The latter implying wind is present, just not affecting the projectile left or right of the target during flight.
 
#19
Re: Spin Drift?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: XTR</div><div class="ubbcode-body">
...sometimes there is just something happening that you can't see, and it does however feel somewhat better to see that the guy next to you cant see it either. :p </div></div>

That's for sure. I needed a full mil left correction Tuesday night shooting out at 980 yards. Thing is, there was no perceptible wind. About .2 mil of that could be accounted for by spinD and the rest proven by the bullet to exist yet could not be seen.
 
#20
Re: Spin Drift?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: XTR</div><div class="ubbcode-body">there is no such thing as a "no wind scenario" <--- OK, maybe someone else has used it but I'm claiming that one till proven otherwise
</div></div>

Fact, I have shot long more than once in a no wind environment.

If you have never had to shoot in Korea very much you would have seen it as well. Far above, an below the 38th is known as the land of the morning calm for reasons other than battle. I have seen smoke from camps both sides of the line that went as straight up as a plum bob for 3-400 feet before there was any movement side ways at all. Just because you have never seen something does not mean it won't happen in other places on this rock. There's a few other places on this rock it happens as well.
 
#21
Re: Spin Drift?

Wow! To me Korea was anything but calm (wind-wise
wink.gif
). So bad in fact that I wished I could anchor myself to the ground and wrap myself in tarp or something. But then I never climbed high there - had other things to take care of.
smile.gif
 
#22
Re: Spin Drift?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mouse07410</div><div class="ubbcode-body">Wow! To me Korea was anything but calm (wind-wise
wink.gif
). So bad in fact that I wished I could anchor myself to the ground and wrap myself in tarp or something. But then I never climbed high there - had other things to take care of.
smile.gif
</div></div>
Don't know where you were, but in 1965 to 75 above an below the 38th, north of the Imjim between Freedom an Libby bridges, It was most always dead calm in the AM. Far north as Nampo an Kosong, I've watch smoke rise like string in the mornings. As far south as C/C "1" I've seen the same thing. Even around Jilin China, many winter mornings were so calm you could find targets via their breath rising.
 
#23
Re: Spin Drift?

I don't have a whole lot of long range experience, but I do get to 1000 yds at least once a month, some months once a week and I've put close to 1400 rounds down range so far this yr. I've never seen a string that didn't require some kind of windage adjustment during the string.

Yea if you're shooting a 7mm RSAUM pushing a 180 at close to 3000FPS you might not notice too much, but 308 at 1000yds moves almost all the way across the 9-ring with only 1 MPH of full value wind.

Yea, maybe it happens somewhere, just not while I'm trying to hit the X-ring at 1000 yds.
 
#24
Re: Spin Drift?

Based on your numbers (I had to guess at a few of the inputs), JBM predicts somewhere in the neighborhood of a 14.5 MOA drop at 725 yd. A <span style="font-style: italic">one degree</span> rightward cant in your scope would cause your POI to shift almost 2" right at 725 yd by changing some part of your elevation adjustment into right windage [(sin 1.0) x 1.0472in/MOA @ 100 yd x 14.5 MOA x 725yd/100yd = 1.92" @ 725 yd]. So although wind and driver are likely explanations as mentioned above, a very slight cant to your scope may also have contributed to the rightward shift in your POI to some degree; it doesn't take much cant to make a difference. There was a very cool thread a few months ago demonstrating this principle where the OP compared groups at 600 yd with the rifle straight, or tilted so the reticle crosshair matched a target that had a line canted at ten degrees from horizontal. Here is the link if you're interested:

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=2601069&page=1

Here is another link previously shared by Lindy to a more detailed explanation of reticle/scope cant:

http://www.microlevel.biz/cant_errors.html
 
#25
Re: Spin Drift?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: XTR</div><div class="ubbcode-body"> Yea, maybe it happens somewhere, just not while I'm trying to hit the X-ring at 1000 yds. </div></div>

Unless you have wind indicators along the height bullet path, it's very hard to find the river of wind that effects the bullet the most. Also once you fire that first shot, unless your having the second one in flight before the sound of the first one goes away, you have to wait for the same conditions for the rest to fly in. The last thing you want to do is chase your last shot, with ever changing adjustments. A .22 LR at 250yds will teach you a lot about reading mother nature, if you apply the same goals.
 
#26
Re: Spin Drift?

Since you didn't mention if you're using a level or not; I think rifle cant came into play.

The reloads? Well, certainly something is going on. Maybe brass had been fired unequal amount of times? Neck or full length resize?
 
#27
Re: Spin Drift?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Gunfighter14e2</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: XTR</div><div class="ubbcode-body"> Yea, maybe it happens somewhere, just not while I'm trying to hit the X-ring at 1000 yds. </div></div>

... The last thing you want to do is chase your last shot, with ever changing adjustments.... </div></div>

I completely understand that; however,

When you look down range, shoot a 10,
look and shoot an 8,
look again, doesn't look like anything has changed, so you think you must have somehow pulled the shot, or it was a bad load
Shoot another 8, in the same spot
Dial 1.25 right
Shoot a 10.

The shooter in the example above better be looking for the switch or he'll shoot one out the other side in a few minutes, but I've done it and I've pulled for it, more than I can count in both cases.

Now obviously the shooter in the case above has missed something, but if it was easy we'd all be shooting 200s with matches decided on X count, but they are not, at least not in TR, or very often in F open for that matter. I've not seen anyone in TR shoot a 200 here in Oak Ridge this year, hell I don't recall that I've seen anyone in TR clean 800 and that's the biggest target you'll ever shot at in F class.


That said, the point of my original post was that I've rarely if ever seen wind conditions so stable that you could fire 10 rounds on target at long range (1000) and not see them pushed around or have to compensate or wait out a switch at some point in the string, and the changes can be really damned hard to see even with wind flags.
 
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