Range Report Spindrift Calculation??

#51
Re: Spindrift Calculation??

Adjust for what ever makes you happy. If you want to calculate spin drift, go ahead. Everybody has to do something with the time they have on the planet.

Might want to consider shooting rather than calculating. Let me pose you a question:
If spin drifts exists at 1000, it must have begun right out of the end of the barrel, Yes?
 
#52
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TiroFijo</div><div class="ubbcode-body">
I'm trying to find out with the CheyTac people if their radar data is just TOF and trajectory, or if it also includes bullet yaw. </div></div>

I will eat my hat if they have more than x, y and z data!


<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TiroFijo</div><div class="ubbcode-body"> If they make the second degree effects calculationes like spin drift based only on TOF then it is going to be pretty inaccurate unless the specific bullet/load/barrel combo is very similar to the "paradigm". This is the case with most other programs. </div></div>

Yes, but better than ignoring it all together as 'too difficult'!

A 30% error on 10" of drift is better than a 100% (ie ignore it) error!


<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TiroFijo</div><div class="ubbcode-body"> IMO it would be nice if they make all this clear in their literature. The radar testing and program features seem like a step above the competition.</div></div>

Or great marketing hype!

Remember the 3 Bs:


Bullshit Baffles Brains.

smile.gif



 
#53
Re: Spindrift Calculation??

Actually Chey Tac has done all those bullets on doppler that are listed in their ABC library but they also have a list that you can use when your bullet of choice isn't on their list. It tells you what bullet from the library to use to use to get your data for the bullet you're using. Now that thye are adding the extra 250 bullets which goes beyond basic military rounds I think it will cover most bullets used by the people here.

Why is it so hard for you people to believe there is a company that is actually putting forth the extra effort to do it right? You should be applauding them and not making assumptions and talking shit about them.
 
#54
Re: Spindrift Calculation??

isn't the sprin drift applied by Chey Tac designed more for a parallel bore set up, and not intended necessarily on rifles with a 100 yard zero (or more) where most of that 'drift" would be dialed out ?

And wouldn't it also make sense that if you dialed in an MOA of left "drift" ahead of time you'd use "less' wind down the line...
 
#55
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rob01</div><div class="ubbcode-body">Actually Chey Tac has done all those bullets on doppler that are listed in their ABC library but they also have a list that you can use when your bullet of choice isn't on their list. It tells you what bullet from the library to use to use to get your data for the bullet you're using. Now that thye are adding the extra 250 bullets which goes beyond basic military rounds I think it will cover most bullets used by the people here.

Why is it so hard for you people to believe there is a company that is actually putting forth the extra effort to do it right? You should be applauding them and not making assumptions and talking shit about them. </div></div>


Doppler radar is a very good tool and a relatively new tool for ballistics but it’s not bullet proof and it’s not an exact science as some may think. IMHO, calculating or trying to calculate spin drift for long range shooting is a waist of time and effort. When you get down to the nuts and bolts of calculating spin drift with or without Doppler Radar there are just too many variables involved for truly accurate and predictable results.

As TiroFijo mentioned earlier, different bullets, different barrel twists are among just a few factors that can and will effect your spin drift calculations. The only real way the Doppler Radar results would be truly accurate and predictable is if the test bullets were fired in an 1000 yard plus environmentally controlled environment such as a climate controlled tunnel with absolutely zero wind. Having a ventilation system in the tunnel that couldn’t be completely sealed off could create drafts that could effect down range results at longer distances. Small ballistic changes yes, but it still factors into the overall equations.

At the end of the day there are just too many factors for spin drift to even factor into your long range shootings. Real shooting data will always be best.

Don't get me wrong Doppler Radar will open up new avenues into understanding ballistics but don't think for a minute it's an exact science...you'd only be kidding yourself.
 
#56
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">isn't the sprin drift applied by Chey Tac designed more for a parallel bore set up, and not intended necessarily on rifles with a 100 yard zero (or more) where most of that 'drift" would be dialed out ?

And wouldn't it also make sense that if you dialed in an MOA of left "drift" ahead of time you'd use "less' wind down the line...
</div></div>
Having talked to Triggerfifty for a few years now and read his book on the .50 he has extensive knowledge on the ABC since he did almost all of the testing for it with EDM and CheyTac and as his book states he always set his rifles up PBZ as the location of the shot and environmental data would have to be taken into account when the team arrived. He explained that he could take a short range shot to verify PBZ and add all data into computer to make the long unknown distance first round hits. Speaking to a few of the people that have shot with him using the CheyTac as well as other .408 and the new .375/.408 the software is dead on to 2200 to 2500 or so yards that is a HELL of a shot at anything smaller than a house in my opinion. He could chime in and add or correct me. His book is a pretty good read and quite technical.
 
#57
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rob01</div><div class="ubbcode-body">Why is it so hard for you people to believe there is a company that is actually putting forth the extra effort to do it right? You should be applauding them and not making assumptions and talking shit about them. </div></div>

Robo,

I don't think anyone is talking shit about them.

What has been discussed is a belief by some that the program uses doppler data for each individual bullet in its library to model drift for each individual bullet. (When I say 'drift' I mean what most here are calling 'spin drift').

Knowing the variables that affect drift, one or 2 folks (incl me) with an understanding of ballistic computation methods have pointed out that that is unlikely.

The explanation Tiro received from the <span style="font-weight: bold">company</span> (as opposed to the opinion of users) is that the program models drift by best-fit mathematical approximation (in their words, they use a "mathematical paradigm or modality"').



Well, that's an entirely honest answer - and just what the common-sense check told us.


And there's absolutely no criticism being made of that method; because that's the only way you can do it in a fast hand-held
smile.gif
.


The only resulting clarification is, I suppose, to disappoint those who may have thought that their little magic box of elecktrickery was doing 6DOF calculations for them
smile.gif





 
#58
Re: Spindrift Calculation??

Guys I'm going on what I got through my expierience with the Chey Tac company in three days of training at Arco and an hour and a half long power point presentation and Q&A on the ABC/CABC. When we got to shooting for the 3 days we used them with the 408, .50 and .308 shooting out to 2000 yards with the first, 1600 with the .50 and 1120 with the .308. Whether you believe it or not the ABC works. Until you get hands on with it you might not believe it so there's no trying to convince you.
 
#59
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rob01</div><div class="ubbcode-body"> Whether you believe it or not the ABC works. Until you get hands on with it you might not believe it so there's no trying to convince you. </div></div>

LOL I have been dealing with that for years now in regards to the ABC, the capabilities of the 408 and 375/408, the environmental conditions that you MUST monitor and calculate for at such ELR distances. I may not like some of the "business" things that Cheytac do on a personal level but results are results.

Thanks
 
#60
Re: Spindrift Calculation??

Jeff, you don't need a closed tunnel to test for spin drift.

With a good radar and EXTENSIVE testing on a range that has several wind/baro meters downrange you get bullet bullet X, Y,Z position and TOF at every point downrange, and also bullet yaw data, separate wind drift and integrate everything into the ballistic model.

It is very difficult and a lot of work to get all the many variables/coefficients required for complete 6DOF caclculations for each bullet/load/barrel combo, and computer run time would be looong. So for normal, flat fire shooting some simplificatins must be made. How "simplified" the models are is anyone's guess, but gieven the time limitations probably the more bullets you test the simpler the method used.

This is a good overview of ballistic programs:
http://bryanlitz.bravehost.com/BalProgs.html

Edited to add: as Brown Dog said, for "normal" shooting up to 1000 m or so just an estimation of gyroscopic drift is better than nothing, and the effect is very small anyway. But for very long range shooting (1200+ m, sometimes with vertical angles) a more accurate calculation is needed since the spin drift value grows large fast and extreme accuracy is needed. I think CheyTac has more extensive testing on some bullets intended for extreme long range.
 
#61
Re: Spindrift Calculation??

Well let me toss some into the arena here.

As Lindy has said spin drift to 1000 and less is so small it wont be a factor in most cases.

Going deeper you will have to adjust for it.

I would bet that using doppler technology they are testing for alot more tracks and conditions and variables then anything else out there. I dont know anyone that would spend that kinda money to test a few basic tracks and jimmy jam the rest of the data. Seems pretty stupid to me.

But to each his own. You have 2 choices take it or leave it. I will tell you this, i have complete faith in only 2 programs as of now and thats Cheytac ABC and the Patagonia Ballistics. Both use doppler to come to there firing solutions and i have used them with great results.


As Rob said we were up there using the ABC and the results were beyond impressive using the ABC. We didnt even work the wind calls vey hard put the wind at the gun in the system and ran that for mid and target winds and we basically had first round hits 90% of the time if we were off it was due to win a quick adjust and it was 2nd round hits. So what ever magic mojo is in the ABC program you can bet it works. Thats alot more then i can say from the BORS system that was lucky to have been hitting on the same mountain ridge as the target.

In the end i guess trust in your gear and equipment that you use will also add you in first round hits. Oh and dont forget practice. Which will lead to confidence.

Also Cheytac is shooting there rounds over Doppler and to what info they give you they give you. There is such things as trade secrets and intelectual property that you probably dont RATE to get or know about. Why should they give up all the secrets so someone else cans steal there product and results.

If you dont want to take the word from people that are using it with success, then go spend the $$$ and buy it and test it out and come give me a full report on your findings. But i will bet you will be walking away like the guys we seen up there in ARCO with there gun, round and system going wtf are we doing wrong!





 
#62
Re: Spindrift Calculation??

My experience:

At under 1000 yards (and maybe this is a hold-over from my iron-sight days) I often use the finer 1/4 MOA wind adjustments that scopes provide (compared to 1/2 MOA irons) to - in actual conditions - add an insurance 'click' of left windage at 500 meters and beyond.

That said, I still don't know why I do it: if it's because of wind, lack of cant with scope, spin drift, or just a bad habit. But on a no-wind day at 547 yards, .223 or .308, I add one adjustment and it seems to work better for me. Or maybe I'm just fooling myself.
 
#64
Re: Spindrift Calculation??

With the results being available at one's feet,I simply do not understand looking elsewhere for the obvious.

There's no "trade secret" involving keeping good records and actually shooting to yield them.



 
#65
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">wonder how many guys are dialing in a bad trigger ?

things that make you go hmmm... </div></div>hmmmmm...could be dialing in inconsistent cheek pressure.

things that make you go back to basics and re-install the iron sights.
 
#66
Re: Spindrift Calculation??

Spin drfit exists. Period.

I need 3 klicks 0.1 mrad each on my 338Lm at 1000 meters if the rifle is previously zeroed at 300m at no wind conditions and there is no wind on the 1000m range (very seldom). Bullet is 250 Scenar at 907 m/s at sea level.

If I do not adjust for spin drift my shots are 30 centimers or 12 inches to the right of my target at 1000 meters.

Of course sometimes the sidewind plays in my favour and cancels the spin drift by blowing ligthly for right to left.

I do not see that I would be better off in not adjusting for the spin drift. Because when I adjust for it and judge the wind correctly I will make hits at known distances at 1000, 1100 or 1200m.

IMHO spindrift does not need to be taken into consideration before 800 meters. After 1000 meters you HAVE to adjust for it or you will have a miss.
 
#67
Re: Spindrift Calculation??

It strikes me, in all this discussion, that 'doppler' is being spoken of as though it were some sort of Holy Grail.


Doppler radar is just a way of tracking a bullet's flight. It doesn't produce ballistic solutions; <span style="font-weight: bold">it's the 3D equivalent of a ruler and a stopwatch</span>!
smile.gif


It can't be used to 'come to a firing solution'.

It can only be used to compare 'predicted' with 'actual' under a given set of conditions.

It is nothing more than a validation (or not!) of predicted results.

So statements such as:
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: NOMAD</div><div class="ubbcode-body"> Both use doppler to come to there firing solutions </div></div>

Should read 'both have satisfactorily compared their predictions against fired data'.

Doppler doesn't create or model the predictions; it just measures a bullets flight in 3D


Having had the opportunity to examine Patagonia data outputs for long range 308 and 338 in varied conditions, I can assert, without doubt, that they are using Pejsa-based algorithms (or something very very very similar).

..the fact that they checked some of their predictions against a doppler measured firing doesn't make their (or cheytac's) version of Pejsa voodoo!
smile.gif



..but then again, shooting's a mind game; and if a belief in voodoo helps, then run with it
smile.gif

 
#69
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TA</div><div class="ubbcode-body">Spin drfit exists. Period.

I need 3 klicks 0.1 mrad each on my 338Lm at 1000 meters if the rifle is previously zeroed at 300m at no wind conditions and there is no wind on the 1000m range (very seldom). Bullet is 250 Scenar at 907 m/s at sea level.

If I do not adjust for spin drift my shots are 30 centimers or 12 inches to the right of my target at 1000 meters.

Of course sometimes the sidewind plays in my favour and cancels the spin drift by blowing ligthly for right to left.

I do not see that I would be better off in not adjusting for the spin drift. Because when I adjust for it and judge the wind correctly I will make hits at known distances at 1000, 1100 or 1200m.

IMHO spindrift does not need to be taken into consideration before 800 meters. After 1000 meters you HAVE to adjust for it or you will have a miss.
</div></div>



A pair shot today at 975 yards with zero wind and zero windage adjustment and zero adjustment for spin drift.
300 SMK 338 Laupa at 2800 FPS


975Yards338Laupa.jpg
 
#74
Re: Spindrift Calculation??

Brown dog, I cant find any of my notes,there is a calculation that was put forth by the armys testing ground at Aberdean, MD.many years ago that had all the variables and how to do the math for most projectiles with BC's under 1.0 . Since the passing of Chet Hamilton I dont know where to look or who to ask for the info, any help would be much appriciated.

Buck Garrett
 
#76
Re: Spindrift Calculation??

Lowlight,

laugh.gif
The table is in metres and confusingly (if you don't have my muddled brain!) <span style="font-weight: bold">0.1mRad </span>clicks (which I would normally round to the nearest whole click)

so, at 1000<span style="font-weight: bold">m </span>the chart is showing 0.36mils ..around 14 inches

at 910m (1000yds give or take) it's showing 0.3mils ...around 10.75 inches
 
#79
Re: Spindrift Calculation??

Buck,

You’ll get ‘close enough for Government work’ with this standard approximation posted by another hide member (apologies, I forget who) a while back:

SpinDrift[cm]=constant * TOF^2.

For the 308 scenar at my mv and twist rate I’m using a constant of 11

If you’re after real ‘wiggly amp’ stuff, I have this (but not electronically), I’m happy to photograph the preceding paragraphs referred to for definition of terms if you wish
Phgh1010172.jpg

 
#81
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Brown Dog</div><div class="ubbcode-body">http://www.longrangehunting.com/forums/f19/up-downhill-corrections-22768/index9.html

<span style="font-weight: bold">Enough said </span>
crazy.gif
smile.gif





..but since non Flat-Earthers maybe interested
smile.gif
:

155 Scenar at 2940fps 1:12 twist average conditions for where I live:

(Spin) Drift Corrections:
spineg.jpg
</div></div>


If I cranked in that kind of wind-age on a calm day (no wind) I would not be able to hit anything. Is your barrel straight?

Seriously do you really crank in 129.6" of wind-age for spin drift? Surely you jest. That is not remotely believable
 
#82
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">Brown dog, you calculate a 129.6" of spin drift for a 308 at 1000 yards...

Seriously ? or are you fucking with people ? </div></div>


He might want to check to see how much curve his barrel has
 
#83
Re: Spindrift Calculation??

jwp475, it is 3.6 clicks x 0.1 mil each = 0.36 mils = 1.24 MOA at 1000 m = 1094 yds...

This is from Longrange1947, a SOTIC instructor and also a member here:

"Spin drift is a known set value that can be dialed in for the given range. As an example, the 7.62mm spins right about .5 moa at 700 meters, .75 at 850 and 1 at about 925. The shooter merely adds this to his gun dope when he ranges his target. Example would be a sequence in which the observer tells his shooter to "place 7 evelvation, 1 click left spin, parallax ball three." Once the shooter is up the observer would give him a wind read and the shot would be made. This is the long dialogue based on no immediate need to shoot. Snap shots are done differently and then it would depend on the time in position and range card info."

If you want to read about it somewhere else:
http://www.socnet.com/showthread.php?t=68894

 
#84
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jwp475</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">Brown dog, you calculate a 129.6" of spin drift for a 308 at 1000 yards...

Seriously ? or are you fucking with people ? </div></div>


He might want to check to see how much curve his barrel has </div></div>

<span style="font-weight: bold">RTFA!</span>

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Brown Dog</div><div class="ubbcode-body">Lowlight,

laugh.gif
The table is in metres and confusingly (if you don't have my muddled brain!) <span style="font-weight: bold">0.1mRad </span>clicks (which I would normally round to the nearest whole click)

so, at 1000<span style="font-weight: bold">m </span>the chart is showing 0.36mils ..around 14 inches

at 910m (1000yds give or take) it's showing 0.3mils ...around 10.75 inches </div></div>
 
#88
Re: Spindrift Calculation??



He laughs the same way going to the bank each time his diehard followers buy his stuff thinking what works for him will work for them.

As long people think they can emulate the success of someone else through shortcuts someone will always be laughing, usually when they look at their bank balance.

As if simply adding 1 MOA to your dope will put you in the winners circle, well I have yet to see it and I look.

For me, its a personal wash because I have never shot in a "no wind" situation so as long as wind blows, spin drift will be lost in the noise, at least that is how I read the conditions downrange...
 
#89
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TiroFijo</div><div class="ubbcode-body">Oh yes, now that's what I call scientific proof...

jwp475, you are right and all the major ballistic laboratories since the 1900s are wrong. </div></div>


Another at 738 yards & no spin drift adjustment

Shooting338Laupaat738Yards006.jpg



Why don't you call or email Gerald Peery owner of Perry Systems ballistics soft ware (producer of Exball) and ask him about spin drift, you might learn something


http://www.perry-systems.com/

IU'm sure that he doesn't know what he is talking about either and all of his targeting software that the Military is useing is also missing the mark
 
#90
Re: Spindrift Calculation??

Doesn't spindrift vary with wind?
Always been my understanding that 1Kyd BR shooters hold off with an x-pattern based on wind.

I don't know. Just askin
 
#91
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">

He laughs the same way going to the bank each time his diehard followers buy his stuff thinking what works for him will work for them.

As long people think they can emulate the success of someone else through shortcuts someone will always be laughing, usually when they look at their bank balance.

As if simply adding 1 MOA to your dope will put you in the winners circle, well I have yet to see it and I look.

For me, its a personal wash because I have never shot in a "no wind" situation so as long as wind blows, spin drift will be lost in the noise, at least that is how I read the conditions downrange... </div></div>


Follow this advice and you can't go wrong IMHO
 
#92
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Brown Dog</div><div class="ubbcode-body">
TiroFijo said:
I will eat my hat if they have more than x, y and z data!
</div></div>

It is my educated position, that if you have x,y,z data from a radar instalation; that you also have x,y,z, and time data. I also suspect that the original radar data is distance, azimuth, and altitude which is then converted to x,y,z.

With x,y,z and time, you can compute all of the velocities and accelerations to the precision (noise level) of the original dataset.
Click to expand...
 
#93
Re: Spindrift Calculation??

Mitch,

I’m not sure ‘educated comment’ meshes with some of the preceding posts
laugh.gif


But, no argument. You're absolutely right. ..But what you've described would only enable 3 DOF modelling and takes no account of the orientation of the projectile itself –and, therefore, no account of the changing forces acting upon it.

To genuinely model (spin) drift you must either have 4 DOF (one additional axis longitudinally through the projectile) or 6 DOF (ie also gather x,y,z data on the movements of projectile itself -in addition to the 3 DOF data defining where it is in space)


Buck,

I'll give the data my best effort tomorrow -apologies, but I've had too much on to get around to it.
 
#95
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jwp475</div><div class="ubbcode-body">

And how much Coriolis correction do you dial in?</div></div>
that would depend on distance and global location and direction of fire.
 
#97
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: The Mechanic</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jwp475</div><div class="ubbcode-body">

And how much Coriolis correction do you dial in?</div></div>
that would depend on distance and global location and direction of fire. </div></div>

And how much would the max be with a 308 at 1K?
 
#99
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rifles Only</div><div class="ubbcode-body">Imagine looking at the bullets flight from the shooters perspective, but the shooter is upside down.</div></div>

Dude, you have a hurricane coming, get out on the tower and dope some 75+ MPH wind so we have it. use your rifle though I dont want the Werewolf getting wet.

Also, see what a spinning hurricane does to your 1000 yard spin drift dope ?
 
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