Range Report Spindrift Calculation??

#353
Re: Spindrift Calculation??

seriously though...I know all you guy's copied and saved that spin drift chart I posted...don't lie...hahahahahahha...LOL...you know you did. You are all closet spin drift calculator's.

It's better to have and not need than to need and not have.
 
#356
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">Chart is useless without the Key Master... </div></div>

Maybe Brown Dog has it...
 
#357
Re: Spindrift Calculation??

Sigh...

Some people are just SOS

JWP, in particular I'm tired of your SOS quips, like a Rumsfeld 'unknown unknown' some people are just too stupid to know they're stupid;

You get your arse handed to you repeatedly in technical discussions across the net, and yet you continue to argue about technical stuff you just don't understand??!

A classic example:

http://www.longrangehunting.com/forums/f19/up-downhill-corrections-22768/index9.html

As to the other SOS...still lots of flawed concepts being bandied around..

Even the explanations of someone with the open source provenance of Trigger are being ignored

I simply can't be arsed to explain anymore.
smile.gif

 
#358
Re: Spindrift Calculation??

Do you have the key? Maybe you can explain the difference in uphill vs down hill angles for rifle projectiles? Your superior intelegence should be able to handle that.
 
#359
Re: Spindrift Calculation??



I believe that you already posted that link before is that all you've got? No I forget you've 10.75 inches of spin drift at 1K, yea I remember now.
 
#361
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KJDrake</div><div class="ubbcode-body">Sorry guy's...I got here late. what's spin drift? </div></div>

Spin drift is when someone brings up a piece of scientific theory or data, and the this group spins the physics around until the whole group drifts off topic.

We are currently seeing about 0.4 mills of drift after 8 pages .....
 
#363
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Captain Kick-Ass</div><div class="ubbcode-body">well I'm glad the spin drift issue is resolved. </div></div>

Don't we all wish? We're not even close! There are those still among us that just won't give up, love to debate and hear themselves think. My grandpap used to say, “them folks are just dumb as a fence post and have the common sense of a nat”.

Then we have the comic relief team stirring the pot and keeping the knuckle heads who love to hear themselves think believing it’s there next opportunity to get their tiring warn out opinions across. Wishing like heck everyone will finally say, “You know your right and we’re all wrong, by gosh we should all start calculating and adjusting for spin drift”. But that would start another 37 page debate at what range we should start making spin drift adjustments. Remember there are those among us that can see their own bullets spin drift, so I’m sure the debate would start at 100 yards.

But NO, comic relief jumps in and stirs the pot some more, and the process start over, to the tune of about 35 or the 37 pages (and growing) being useless information.

Me I'm just waiting for post #400 so Todd can come out and service my AC for free! 362 and counting. Todd I promise to have cold beers waiting!
 
#365
Re: Spindrift Calculation??

The point here is not if Spin Drift exists in rifle shooting but is this the shooting discipline that can adjust for it.

For those that shoot in these "tactical" competitions know very well all the stress's that are present during any one stage of fire. It's very difficult to even have half of your shit together before you break the shot. If you can't even get the fundy's together in the time allotted how can you adjust for Spin Drift.

For those LR BenchRester's with the concrete tables and 50+ pound rifles...sure I bet they look at everything before they squeeze one off...because they can. That discipline as well as a few others could take every single factor into the equation.

This "crowd" simply does not have the time to worry about it when there are so many other factors that we need to concentrate on. I am sure SD exists as well as most everyone here...but I miss for reasons much more simple than Spin Drift. I pray for the day when I reach a skill level where I take into consideration the effects of Spin Drift...I truely do.

I'm sure somebody has already typed something similar but haven't yet had the time to read all of this thread. My battery on my laptop keeps going dead every 10 pages...LOL.

So you guy's that read the books and have studied this condition from other places...thank you for passing on the info. I try to expand my knowledge base. Just don't take it to personal when us cavemen club you over the head with our shooting experiences. The guy's at the top of the food chain that show up at these matches aren't worried about spin drift...and if they aren't...then we aren't.

smile.gif


--KJ
 
#366
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Captain Kick-Ass</div><div class="ubbcode-body">I guess there is no other recourse other than filing suit against Chad for starting this post. </div></div>

Now I know who started this shit!
 
#367
Re: Spindrift Calculation??

How more posts do we need to all get free AC ?

I am going to use the previously posted chart for SD tomorrow at the Prairie Dog match and I have printed the JBM with the addition of Drift and Magnus, so I'm expecting big things, if not, I am never using it again.
 
#373
Re: Spindrift Calculation??

No, they canceled the match do to rain, but like I said, comparing the windage adjustments with the JBM link you provided had a big change in windage, as much as 1.7 MOA difference between left and right wind at 1000 yards..

Seems like a bit much, although I admitted I could have inputted the information incorrectly.
 
#374
Re: Spindrift Calculation??

The foremat is confusing to me.
The 1.7 moa difference is alot for sure. Was your input for a 175smk .308win or something different?
 
#376
Re: Spindrift Calculation??

The old Z charts did show a difference between 3 an 9 wind for R/H twist barrels but I don't recall it being that much. I have and old chart somewhere from the 80's and it's a little different from the one posted, as the Z was rotated more clockwise, IIRC. The data key is was on the reverse of it as well. I'll have to look/dig for it.
 
#377
Re: Spindrift Calculation??

Well if I still have it it's hid good.
Looking at the Z thats posted I do believe the #6 wind was closer to 1300 as I recall the Z to be inline with 1300 and 1700. The twist was 1/12 with 173's at 2550 IIRC.
 
#379
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Captain Kick-Ass</div><div class="ubbcode-body">I was gone all weekend. Glad to come back and see yall have got this whole issue worked out. </div></div>

LMAO....luckily I shoot poorly enough that spindrift corrects itself when I flinch.
 
#380
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Captain Kick-Ass</div><div class="ubbcode-body">I was gone all weekend. Glad to come back and see yall have got this whole issue worked out. </div></div>

Yes we did, the final answer was classified E/O. I could tell ya but,.. well you know
grin.gif
 
#383
Re: Spindrift Calculation??

"For example (typical 1000 yard small arms trajectory), if you always shoot in the northern hemisphere where the horizontal drift is always to the right, and you have a right twist barrel as most of us do, then your bullet will drift to the right approximately 9" due to gyroscopic drift, and an additional 2.5" due to Coreolis, resulting in 11.5" right drift, even in zero crosswind. However, if you had a left twist barrel in the northern hemisphere, gyro drift and Coreolis drift would partially offset each other, resulting in only 6.5" drift to the right. What's that mean practically, to competitive target shooters? I can think of only one answer:"

if there is no spin drift then why does this guy write about it on his website?

 
#384
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rem_.308</div><div class="ubbcode-body">"For example (typical 1000 yard small arms trajectory), if you always shoot in the northern hemisphere where the horizontal drift is always to the right, and you have a right twist barrel as most of us do, then your bullet will drift to the right approximately 9" due to gyroscopic drift, and an additional 2.5" due to Coreolis, resulting in 11.5" right drift, even in zero crosswind. However, if you had a left twist barrel in the northern hemisphere, gyro drift and Coreolis drift would partially offset each other, resulting in only 6.5" drift to the right. What's that mean practically, to competitive target shooters? I can think of only one answer:"

if there is no spin drift then why does this guy write about it on his website?

</div></div>

Here we go again another one size fits all spin drift effect/calculation for all bullets and bullets types out to a 1000 yards. Please go back and read the last 38 pages of almost useless information.
cry.gif
And yes we all agree spin drift exists.

At least you're getting us closer to post number 400 so Todd can come service my AC for free!
 
#385
Re: Spindrift Calculation??

Just hang in there, most of us are here to learn.
The few that can put a end to this thread have not spoken on this subject yet,... but I think the hammer is coming. I would not miss this next block, for nothing.
grin.gif
 
#387
Re: Spindrift Calculation??

With reluctance, I'll try may hand at this.
I've been an occasional visitor to these pages and have been tempted to post a few times, but avoided it because of the intense pissing contests that always seem to ensue when any technical information is presented.

After recognizing some text taken from my website earlier in this thread, I decided to jump in and see what happens.

Since this is my first post on this forum, I'll briefly introduce myself:
Name: Bryan Litz
Age: 29
Occupation: Aerospace Engineering (specifically air-to-air missile design)
Secondary occupation: I run a part time consulting business called Applied Ballistics, LLC. Primary jobs are designing bullets, writing ballistics software, and external ballistics testing. Don't bother searching for a website for Applied Ballistics, LLC, I haven't made one.
My personal (shooting) website is: http://bryanlitz.bravehost.com/
Shooting related activities: I'm very active in NRA long range target shooting. Highlights this year include winning the Midwest Palma match in Lodi, WI and winning the Palma individual match at the Long Range Nationals at Camp Perry Ohio.
Family: I've got a wife, two step kids, a 5 month old baby, and a black lab.

Here is my understanding of spin drift, first from an engineers perspective, and then from a shooters perspective.

The engineers explanation:
Spin drift, also known as gyroscopic drift, is an aerodynamic effect that's caused by the bullet's axis of rotation lagging behind the velocity vector as the round rotates thru the arc on a long range trajectory. Right hand twist barrels will result in a slight nose right orientation, and vise versa. The following variables affect the magnitude of spin drift:
Bullet length: Longer bullets have more spin drift because they produce more lateral 'lift' for a given yaw angle.
Spin rate: faster spin rates will produce more spin drift because the nose ends up pointing farther to the side.
range, tof, trajectory height: spin drift increases with all of these variables.
There is another kind of drift related to the spin of the earth, known as Coreolis drift. Coreolis drift can be up, down, left or right. Unlike spin drift, Coreolis drift is not an aerodynamic affect. It's a result of flying from one point to another across the surface of a spinning sphere (earth). The direction of coreolis drift depends on your location on the sphere, and the azimuth your shooting. The magnitude of the drift depends on the location, azimuth, and time of flight.
The two kinds of drift (spin drift and coreolis drift) are not related. Similar to gravity drop and wind drift, they're two separate effects that have to be taken into account individually, and quantified with their own respective variables.

Spin drift from a shooters perspective:
First of all, for any application where 'sighters' are allowed like most styles of target shooting, the effects are irrelevant because the spin drift is exactly the same for each shot. Once the sights are zeroed for a particular range, it's a non-issue. However, given the title of this website, there are applications where sighter shots are not allowed. In tactical situations where the first shot has to be accurate, all of the variables have to be accounted for before taking the first shot (unlike target shooting where you can 'dial out' the bias).
When you get down to it, it's very hard to isolate the effect of spin drift in the field. Let's say, for the sake of argument, that spin drift is worth 1 MOA at 1000 yards. Just Given the uncertainty in the crosswind, spin drift already is approaching 'insignificant'. Also consider how level the scope has to be, and how perfectly vertical it has to track in order to justify worrying about such a small lateral deflection. Given all these real world variables, it's no wonder there's such a diverse opinion about the effects of spin drift. Everyone sees the effects thru a different convoluted set of other dominant variables.
So should tactical shooters worry about spin drift? Even given the above considerations, I think it's still wise to apply corrections for effects that are present. You're improving your chances that the shot will be more centered than if you don't account for the real effect, even if you miss for another reason. It's poor planning to ignore real effects, and just 'hope' they all cancel each other out in the end.

As far as how to calculate spin drift...
It's not easy. The only free resource I know of is the online JBM code referenced earlier. Given the complexity of spin drift, it should be no surprise that the list of inputs is long, and they're not all easy to get. For example, the axial and transverse MOI's, ogive radius, etc. I've not personally verified the spin drift outputs of the JBM code, however, I can vouch for some of the other JBM products; they're solid. I'm confident that if all the right inputs are entered, it will give you as good an answer as anything else. Obviously, if you guess on half the inputs; garbage in - garbage out.

These are my thoughts on the subject. I'm always open to criticism but I'm not going to engage in any pissing contests here. The facts I've presented on spin drift and coreolis drift are pretty basic, text book stuff. The interpretation of the facts, and how they can be applied is the interesting part that some debate can be expected.

Take care,
-Bryan

 
#390
Re: Spindrift Calculation??

Bryan,

Great info, thank you.
I do have a question if you don't mind. Would the firing angle, relative to horizonal, have anything to do with the amount of drift given the same launch data?

Thanks,

Kenneth
 
#391
Re: Spindrift Calculation??

Kenneth,
The short answer is:
Yes.

The reason is: The drift happens because the trajectory is arcing due to gravity. You get a yaw of repose from the arc, and spin drift from yaw of repose.
If you shoot straight up or down a plumb line, the trajectory will have no arc, no yaw of repose, and no spin drift.
In between horizontal and vertical fire, the spin drift diminishes with the cosine of the angle of fire.

-Bryan

 
#392
Re: Spindrift Calculation??

Bryan,

Thanks for your insight on spin drift. You said what a few of us have been saying for almost 40 pages, but you were able to break it down better in technical terms.

I would hope this would put this subject to rest and we could move on, however there are still those out there waiting to be heard...again that won't give this up.

They're still bound and determined to make a case for why it all so important that we should be factor in spin drift for our long range shooting.

Oh well getting closer to #400 post. This will make #391, good thing it stays hot here in Texas into the end of Oct and early Nov, I might still be able to my AC serviced by Todd afterall.
 
#393
Re: Spindrift Calculation??

Jeff,

Re-read:

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bryan Litz</div><div class="ubbcode-body">So should tactical shooters worry about spin drift? Even given the above considerations, I think it's still wise to apply corrections for effects that are present. You're improving your chances that the shot will be more centered than if you don't account for the real effect, even if you miss for another reason. It's poor planning to ignore real effects, and just 'hope' they all cancel each other out in the end. </div></div>

smile.gif
 
#394
Re: Spindrift Calculation??

Hey, it's friday, before a holiday, I'll continue to play.
smile.gif


Brown Dog, I think you left out a very important part of your quote there of Bryan's post. Taking a bit farther:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">First of all, for any application where 'sighters' are allowed like most styles of target shooting, the effects are irrelevant because the spin drift is exactly the same for each shot. <span style="font-weight: bold">Once the sights are zeroed for a particular range, it's <span style="text-decoration: underline">a non-issue.</span></span> However, given the title of this website, there are applications where sighter shots are not allowed. In tactical situations where the first shot has to be accurate, all of the variables have to be accounted for before taking the first shot (unlike target shooting where you can 'dial out' the bias).
When you get down to it, <span style="font-weight: bold">it's very hard to <span style="text-decoration: underline">isolate the effect of spin drift in the field.</span></span> Let's say, for the sake of argument, that spin drift is worth 1 MOA at 1000 yards. Just <span style="text-decoration: underline">Given the uncertainty in the crosswind, spin drift already is approaching <span style="font-weight: bold">'insignificant'.</span></span> Also consider how level the scope has to be, and how perfectly vertical it has to track in order to justify worrying about such a small lateral deflection. Given all these real world variables, it's no wonder there's such a diverse opinion about the effects of spin drift. <span style="text-decoration: underline">Everyone sees the effects thru a different convoluted set of other dominant variables.</span></div></div>

Now, I underlined and highlighted the parts I felt were of particular importance and I ask the following follow up questions.

Where did you, and for that matter others, get their data, I would probably say, "in the field". So, note the response to that method of gathering data.

Second, the information posted regarding the input of data to JBM, and what level the user has to go through... pretty detailed information next to what no one has handy.

I would personally want to know what direction people's ranges are set up, and what direction the prevailing winds are coming from to make an initial determination on their data. Then I would want to see them shoot, to gauge their level of trigger control and follow through before giving any credit to their findings. As demonstrated in more detail than this thread has done, I think the shear number of shots pulled to the right beyond a 1/2" at 100 yards has to be accounted for... the targets are all over this site, the evidence in my opinion is strong.

Remember, garbage in, garbage out...
smile.gif
 
#395
Re: Spindrift Calculation??

Brown Dog and TiroFijo are both right about SD. I wish we could have all necessary equipment needed to observe and measure SD. I do apply corrections for the SD and will continue doing so until the law of physics change.
Bryan said it right all the way, dough he also said that some other factors decrease influence of SD. It's not my fault some people have flawed wind reading technique.
I have no desire to argue with anyone here about anything but I notice a trend some shooters believe they picked up all the knowledge in the world.
I saw too much colorful answers here and I wonder how many of those posters ever tried to hit anything beyond 600yds. They just agree with the bunch. Oh, he is 1k shooter, he had to be right plus it's cool to support cool guy like him on the forum. Thats just lame and ain't helping, but that do make you look .... .
I learned a lot from the shooters who were worse than me on the range. Being a good shooter do not qualify you to know everything.

thunder11
 
#396
Re: Spindrift Calculation??

thunder, you must be a World Class shooter to come in with 3 posts and claim, your addition of a SD correction is definitely making it right and anyone not is wrong...

But, hey, you have your opinion as do the rest of us. Personally, I'd go spin drift less against you any day of the week, and I'm sure my skills behind the trigger as well as reading the wing will carry me quite far without a 1 MOA bandaid.
 
#398
Re: Spindrift Calculation??

Yeah, it sucks when you have just 3 posts. And no, I'm no world class shooter, but I know very well what I'm talking about. But I'm sure you do too.
What bothers me is that this thread reached 10th page but I saw only 10-15 really good posts on both sides. Rest of the posts were posts of "supporters" who don't think with their heads because it's easier, safer and coolier to support good shooters and this forum has quite few. The truth is that they just ruined good conversation.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: "Lowlight"</div><div class="ubbcode-body">Personally, I'd go spin drift less against you any day of the week, and I'm sure my skills behind the trigger as well as reading the wing will carry me quite far without a 1 MOA bandaid.</div></div>
Same here. However I will cut and paste something I said to some other member who posted in this thread.
"While their wind reading technique is wrong it somehow compensate for spin drift, but as they go beyond 1k they will face major problems hitting anything for the same reason they "hit" their targets at 1k." --- Posted 08/05/08
Now, since you decided to quote Mr. Litz I will do the same by quoting only the part you underlined :
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: "BryanLitz"</div><div class="ubbcode-body">Just Given the uncertainty in the crosswind, spin drift already is approaching 'insignificant'.</div></div>
Everyone here agreed that wind is the most difficult variable we have to compensate for when in the field. Since you all integrated SD in your wind charts that doesn't mean that influence of SD is any less. Thats because SD has nothing to do with wind, dough we do have to adjust the same knob on our scopes. Now, this is the part where we disagree. You admit that SD drift exists but it's not that important until we try to shoot further than 1k. Ok, I can live with that, but please tell us how you will compensate for SD at 1.5k. I would really like to hear yours on this one.

thunder11
 
#399
Re: Spindrift Calculation??

Approach my shooting at distance from three perspectives...

1, I consult my PDA, in this case I have a Palm with a Horus Chip that includes an option for SD and Coriolis for extended distance shooting.

2. I look at the wind, and see how that relates to my shot. SD In not included in wind holds, however in situations where the wind component is stronger than the SD component I find that the wind is usually the right number. I am sure there is a scientific reason for this to satisfy the proponents of SD use.

3. My Fundamentals, at this point, I have time on my side, and honestly if I was to fall back my USMC experience and training, if I was put militarily back into that situation today, i would be turning the dials on my radio and not my rifle. But since you asked about the shot, the fundamentals have to perfect, and thanks to that distance I have "time' on my side to set up the shot, note the changes in the wind as it never moves but gusts and blows... so that is going to be a deciding factor does the wind out weight the SD.

I have shot this to much success, but I do tend to shoot a lot inside 1000 with just as heavy a focus on the fundamentals so when I am shooting farther I tend to do so very well. I think the two go hand in hand. My mantra at distance is "trigger, Trigger, trigger..."

but I don't use arbitrary numbers, like say, 1 MOA @ 1000 yards because it's easy and has been rounded up for convenience. I find it strange all the proponents seemed to have reached the same conclusion and number given the different systems employed when clearly the science acknowledges a difference.

 
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