Range Report Spindrift Calculation??

#252
Re: Spindrift Calculation??

Experiment: Parallel bore zero or point blank zero. Then shoot to 100 yds. If elevation is only change, SD is not a factor. If it does move to the right then SD could be plausible.

I am like Mike to an extent. I put on .5 at 600, .75 at 800, and 1.0 at 1k left windage. Groups always seem to be right of target for me personally if I do not do this. I am not new to shooting long range and have fired thousands of rounds at that range with different cartridges. I am not trying to toot my own horn, just stating that I have a little experience that makes me question the why.

Now for some questions and statements that there are no answers that I know of:
1. It would seem that as the bullet slows, SD becomes more pronounced. Why?
2. SD should increase as twist rate increases, but what if the slowing of the bullet's spin actually causes the bullet to "dig in" to the air around it. A faster twist then might decrease spin drift.
3. Would surface texture of the bullet change this? I am thinking of dimples in golf ball
4. I would also think that at higher altitudes SD would be less.

Just my thoughts. Flame away.

BTW, I found a top, spun it to the right, top moved slightly to right. Spun to left, top moves slightly left. I know this is worlds apart but just something that happened to be handy.
 
#253
Re: Spindrift Calculation??

so... if the minuscule amount that occurs at 100 yards actually gets compensated for by zeroing the weapon, would not that correction expand as does MOA to a certain distance?

therefore, no correction needed?
 
#254
Re: Spindrift Calculation??

HOLY SHIT this post has detoured into an "I do so you do or I dont so you dont".

Here are my questions once again:

For the crowd that says just zero and those distances and be done with it but still say they dont account for spin drift:
1. Check your "zero" for 100yard target and then check your 1000yard target, Now check to see if you had to adjust the windage settings and if you did then what way are they adjusted?
2. Check your "zero" for 100yard target and your 1000yard target in a 10mph wind from 3-9oclock and from 9-3oclock values, Now are your "wind" reading adjustments identical for the same mph wind from both directions? If not which side requires less "wind" adjustments?

For the crowd that says it doesnt exist no matter what:
1. I would suggest various reading materials on aerodynamic and spin stabilized flight.

For all others:
Here is my take for sake of this discussion.
1.I DO use ballistic program that accounts for it.
2.I use a muzzle zero (thats a complete other discussion that could turn into same type as this one has lol)
3.Here is why I use and say it must be accounted for (do I have the "end all" formula? No cause so many things change with it, thats why I use a program that was pretty much written STRICTLY for the projectile I shoot). Its all a percentage of errors that are totaled to decide of shot is good or no good. If I can reduce that percentage by opting to account for spin drift then it does 2 things..1-It lowers my overall error percentage and 2-It allows me to make that error percentage somewhere else and still be under the percentage allowed for shot to be good.

Thanks
 
#257
Re: Spindrift Calculation??

Hey, through this one into the mix...

Do you really think a 5MPH wind is constant from your muzzle to the paper?

Sheesh. 26 pages of yahuu & nahuuu.

All the math in the word does not mean jack if you never shoot.

Just shoot the f'en thing. 'Cause in the end, a miss is a diss and hit is legit.
 
#258
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">All the math in the word does not mean jack if you never shoot.

Just shoot the f'en thing. 'Cause in the end, a miss is a diss and hit is legit.</div></div>

That is what I am saying, I get to walk out my door and shoot, and in some cases, paid to shoot. I don't sit around thinking about shooting reading books with formulas you can't even begin to use.
 
#259
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">
I don't sit around thinking about shooting reading books with formulas you can't even begin to use. </div></div>

german2.jpg

What about shooting German books???


 
#260
Re: Spindrift Calculation??

I am a total dumbass on the spin drift theory here but have a few questions that maybe someone can answer...

Since it seems Spin Drift occurs, to some extent, during the entire flight of the round... would the problem occur
at a greater degree when the round goes trans sonic because the bullet is then over stabilized?

Would this cause the bullet to fall nose high and present a greater surface to the air resistance?

Does the sonic shock wave protect the bullet from excessive spin drift early in flight?

I read where some cant the rifle or cant the scope to allow for Spin Drift. If I placed a rifle in
a vice and rotated it 90 Degrees to the left would my POI then be high or still to the right??

I recently did some dope tests on 308 175 FGMM at 1000 yards and never allowed for SD and shot a 10 shot
group of 9.1+" with a DPMS SASS Rifle.

Wind was at 330* (11 o'clock) with an average of 3 mph. This was taken at 0 , 500, and 1000 yards using 3 Kestrel
4500's.

Used Exbal to figure elevation and windage. If SD were 1 MOA @ 1000 yds would I not have missed my target
(18" x 18") completely at this distance?

All shots were close to center mass on target and just a tad high.

Just tryin to learn a little here.....
grin.gif
 
#261
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Huckleberry</div><div class="ubbcode-body">CKA, that is a real good question. SD seems to increase with range. More than the initial correction. Why I don't know. </div></div>

Spin Drift DOES increase with range. The most SD is past the max ordinate of the shot. That is because the round is carrying it's nose high, and is presenting "more" of the projectile to oncoming air resistance. As I explained before, the lower air pressure on the lee side and the bottom of the bullet is the direction the bullet will drift. As this pressure is greater when the bullet is not correct attitude wise (over stabilized, carrying the nose high), the drift is greater in the direction of lower air pressure.

The mathematical formulas used in the Cheytac ABC are super enhanced formulas that derive data material from the Doppler radar tests, I know because I provided those formulas and interpreted the radar data from 2001, 2002 and ...

In this image, you see the effect of supersonic to subsonic transition on a LONG bullet, the 300 gr. Sierra Matchking 338 cal. The VLD designs have even a greater problem with excessive SD. Controlled spin, LRBT / Hooker / Cheytac bullets when shot down a correct barrel exhibit about 78 - 92% less SD. That too has been verified by Doppler.

keyhole1.jpg
 
#262
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">where did I put "hear" I can't find it...
</div></div>

OK beside spin drift we now have spell check. CKA my college professor would be proud.
cool.gif


This topic has gone on now for 26 pages. Many think that spin drift should be accounted for, many think not. And to think this all started from someone asking for a free program that would calculate for spindrift.
 
#264
Re: Spindrift Calculation??

The very best part of this whole thread is the true, inter thoughts of many who responded, and those that did not.
Ask questions long enough an the results, may brighten up the forrest, so one can see the trees for what they really are.
 
#265
Re: Spindrift Calculation??

Dean,

I see with the 250gr Lapua at 3000fps the spin drift correction for 1800 yards is .8 MOA... which in my mind sounds about right.

How does that jive with the idea that people are not widely using 1 MOA with a 308 @ 1000 yards and still hitting targets. Shouldn't the 10" or even reported 11" difference create a more serious issue ? Reference Elkhunter's post above for example of a common experience.

Besides the 7 variables you posted earlier, if SD is present to that degree shouldn't it not only mess with no wind situations but with wind tables in general, leaving the shooter long or short depending on the wind direction. By all accounts enough to miss a target consistently.
 
#266
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...shouldn't it not only mess with no wind situations but with wind tables in general, leaving the shooter long or short depending on the wind direction.</div></div>

No - because no one and no system can measure the wind over the course of the bullet flight to a resolution of 1 mph, unless he's got a pure headwind or tailwind. When a guy misses, he just figures he blew the wind call <span style="font-style: italic">a little</span>, and corrects it on the next shot.
 
#267
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...shouldn't it not only mess with no wind situations but with wind tables in general, leaving the shooter long or short depending on the wind direction.</div></div>

No - because no one and no system can measure the wind over the course of the bullet flight to a resolution of 1 mph, unless he's got a pure headwind or tailwind. When a guy misses, he just figures he blew the wind call <span style="font-style: italic">a little</span>, and corrects it on the next shot.
</div></div>

So Lindy, how does that affect the reverse, you Kestrel the wind, and say it is light, 5MPH, you input the data or use your table and you get a first round Hit close to center... you blew the call as well within 1 MPH ?
 
#269
Re: Spindrift Calculation??

Frank I think a man can get into trouble just taking a Kestrel reading as not many ranges have a constant wind from ffp to impact areas. When I talk about zero wind I am reading Mirage at several locations between the butts and my position. For low winds I find Mirage far better indicator than a Kestrel.

Kestrel is nice for higher winds but that 0-7 mph is hard to beat mirage reading for.

I still dont think the drift is much for less than 1000 yards and shooting steel wont show because a splash hit 5" off center looks like a center hit anyway.
 
#270
Re: Spindrift Calculation??

Mike, you know what I mean, if you use 5 wind flags to estimate the wind, whatever...

Basically, it comes down to shear luck... you either blow the shot by exactly 1 MPH to hit, or you miss. that is what I am getting at...because otherwise it wouldn't work.
 
#271
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tactical</div><div class="ubbcode-body">Frank I think a man can get into trouble just taking a Kestrel reading as not many ranges have a constant wind from ffp to impact areas. When I talk about zero wind I am reading Mirage at several locations between the butts and my position. For low winds I find Mirage far better indicator than a Kestrel.

Kestrel is nice for higher winds but that 0-7 mph is hard to beat mirage reading for.

<span style="font-weight: bold">I still dont think the drift is much for less than 1000 yards and shooting steel wont show because a splash hit 5" off center looks like a center hit anyway.</span> </div></div>

I don't know what you are shooting but I can see where the point of the bullet hit on the steel that I shoot

DSC00857.jpg



OMG I forgot to add in the spin drift

338LapuaBrassSolid011.jpg
 
#272
Re: Spindrift Calculation??

Frank I know what you mean and knew you meant more than one reading location but someone reading this wont.

Me I could care less what a man does as long as it works. As I said for steel I dont worry. Its only for that little tiny X ring

JWP and that shows exactly what? I have more than a few targets where I center punched them myself. My point was a hit seen through scope at 1000 yards will not show splash within .5 moa. If you are telling me you can watch splash that well while shooting I am all up for what you are using for scope and conditions where mirage allows that clear of view. I have more than a few 1000 rounds down a 1000 yard range I cant see splash that finely. Maybe you can but I cant As to what I am shooting? Lots of different rifles but mostly a RPA with 30" 1x12 twist, in 308 with 155 Scenars around 3050 fps. I use that a bit for F TR Class. Come on out its fun.
 
#274
Re: Spindrift Calculation??

JWP for hitting in field I dont use it to 1000 either because as said so much other crap burns you no time to worry about that.

For field I just dial range and hold wind. I dont think Frank, you or I disagree in this area at all.

My only reason for joining this discussion is I would like to see how the f to actually figure it for extreme range and with different calibers and loads. If its a math equation I just want formulas. Has to be some formula that takes in spin rate and mass to come up with what happens. I cant see use of radar for each round and velocity
 
#276
Re: Spindrift Calculation??

Mike,
I don't know that you could predict SD perfectly due to so many variables, but we should be able to at least get an idea with enough rounds down range. It would be nice if we could get a long range F class match somewhere in the country, Whittington Center maybe, that shooters could start going to 1500 or so. reduce the # of record shots to 12 or so to keep barrel life within reason and it could be doable.
 
#278
Re: Spindrift Calculation??

Fer crying out loud guys, THE FORMULA IS THERE. What you probably can't find is some of the specifics like "K" Factor, and S (v) and S (V) and some other keys. SD is not a simple multiple entry formula, known data is required. Mike, we DID do doppler shots on all those bullets, some 800 so far. And yes, we did get X, Y and Z coordinates with winds removed for everything. It's all part of the Cheytac ABC. Which I have no interest financially in by the way, left that organization years ago, but I do know what's in the ABC software
smile.gif
 
#279
Re: Spindrift Calculation??

Tell you what, tomorrow i'll post the formula in it's entirety, won't do much good though, other values are needed that are taken from coordinate data. Don't mean to stir the pot, every data table i generate (which isn't many lately)
smile.gif
has SD calculated for specific bullets, twists, etc.

Trigger

Have a nice day, i'm tryin to!!
 
#281
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Triggerfifty</div><div class="ubbcode-body">Fer crying out loud guys, THE FORMULA IS THERE. What you probably can't find is some of the specifics like "K" Factor, and S (v) and S (V) and some other keys. SD is not a simple multiple entry formula, known data is required. </div></div>
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Brown Dog</div><div class="ubbcode-body">
Stability calculations require data gathered from firings (such as the dreaded Doppler!)....and they will only apply to that proj at that mv at that spin rate.
</div></div>

Hmm, seems some of us are saying the same things
smile.gif


Good to see one or two posts from others who understand the topic too (I know there are several more of you out there -although, more sensibly than me, choosing not to get involved in this train crash!).

Particularly impressed by Tactical's astute interpretation of his range records data set.

Also, Lindy, notwithstanding your stance on 'noise', delighted to see this from you (the bold emphasis is mine):

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...shouldn't it not only mess with no wind situations but with wind tables in general, leaving the shooter long or short depending on the wind direction.</div></div>

No - because no one and no system can measure the wind over the course of the bullet flight to a resolution of 1 mph, unless he's got a pure headwind or tailwind. <span style="font-weight: bold">When a guy misses, he just figures he blew the wind call <span style="font-style: italic">a little</span>, and corrects it on the next shot.</span> </div></div>

Other than that, my main learning from the 'naysayers' on the thread thus far amounts to the following:

<span style="font-weight: bold"><span style="font-size: 14pt">Anyone who understands ballistics is a book-nerd who clearly shoots far less than the people who have no understanding</span>.</span> Or something along those lines
laugh.gif


<span style="font-weight: bold"><span style="font-size: 14pt">Tube launched spin-stabilised projectiles fly differently when called 'bullet' than when called 'shell'</span></span>.

<span style="font-weight: bold"><span style="font-size: 14pt">Infantry texts on ballistics are authoritative</span></span> (such as the take on humidity posted earlier)
crazy.gif



Trigger,

Before posting more formulae (I posted some on page 8).......there's a yawning conceptual gap between the 'understanders' and the 'non-understanders'.......

I think a bit of 'Janet and John' text and pictures explaining the Yaw of Repose etc would be prudent!
smile.gif
 
#282
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Brown Dog</div><div class="ubbcode-body"> I think a bit of 'Janet and John' text and pictures explaining the Yaw of Repose etc would be prudent!
smile.gif
</div></div>

Man, don't throw out words like, "Yaw of repose" I don't have that much popcorn.
grin.gif
 
#283
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Gunfighter14e2</div><div class="ubbcode-body">Man, don't throw out words like, "Yaw of repose" I don't have that much popcorn.
grin.gif
</div></div>

laugh.gif
 
#284
Re: Spindrift Calculation??

Brown dog, go back and read what I said, I understand ballistics just fine, and I'm not a dumb ass like you but actually schooled trained. -- Hence the noise.

You actually agreed with me when you thought you were disagreeing with me. But because you have taken a hit and run approach to reading you feel you are saying something new.
 
#286
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Brown Dog</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">I'm afraid that anyone who believes that the effect of spindrift on a 175SMK at 1000 yards is 11.43 inches needs a lesson in experimental error.
</div></div>

No, they need a lesson in ballistics
smile.gif
.

</div></div>

here is where Brown Dog said Triggerfifty needed a lesson in ballistics.... too.

And I guess you missed that part on manuals where I posted the errors.
 
#287
Re: Spindrift Calculation??

LL,

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I understand ballistics just fine, and I'm not a dumb ass like you but actually schooled trained. </div></div>

Oh
laugh.gif


You're taking this all far too personally. I'm surprised that you feel the need to launch playground insults. Lighten up, it's a chat.

As I said, I'm not getting drawn into name calling (although according to you apparently I'm now been elevated to a dumb ass as well as a book nerd
laugh.gif
:D)

Ho Hum.
laugh.gif



<span style="font-weight: bold">However, I must take issue with your misquoted allegation that I stated Trigger requires a lesson in ballistics.

<span style="text-decoration: underline">I emphatically did not.</span>


If you reread the piece you have (deliberately?) misquoted; my point was that anyone who believes you can state the (spin)drift for all 175gr 308 bullets as a fixed value requires a lesson in ballistics.

I am in absolutely no doubt that Trigger understands that fact. </span>



However, I would contend that you still believe it's possible;

and this relates to your signal failure to conceptualise the ballistic concepts at play here.

This is compounded by your apparent inability to recognise your knowledge gap.





You can lead a horse to water, but you can't make it drink.





 
#288
Re: Spindrift Calculation??

Please, misquoted you... no, it was direct quote. I misquoted nothing.

I and have no knowledge gap, I have stated my contention clearly on previous pages, and even responded to you in numbers when asked what I believe the number represented... go back and read it.

Finally, its others using blanket numbers which you yourself agree is not correct that I have issue with and was trying to get them to show how a blanket statement could possibly work. 1 number for every rifle doesn't work, which you yourself said.

But you've swung in the breeze 3X in as many pages.
 
#290
Re: Spindrift Calculation??

LL,

This is futile. I'm sure we'd be pals over a pint.


But just to be clear one last time:

The data was originally quoted as X inches drift for a 175smk out of an M24. Fine.

That data will only apply to another 175smk fired at the same MV from another identically spec'd M24. Fine.

You have changed that to 'a 175smk drifts X inches'. Not fine.

Change it to 'a 175smk fired at the same MV from the same weapon etc' we'd be back to 'Fine'.

That subtle difference means everything in terms of conceptual understanding.
 
#291
Re: Spindrift Calculation??

Well, not futile if you read everyone else's response who said, that, "it was their understanding that number was correct with their rifle" when you take my statements out of context you get incomplete information. Hence my point... it's not fine for another 308.

So, tell me about 5 degrees ?
 
#293
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Brown Dog</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">While you're so understanding of all things ballistics, why don't you explain your statement on 5 degrees of temperature change causing a shooter to miss... </div></div>

laugh.gif
laugh.gif


Why are you so affronted that maybe, just maybe, someone else might know more about this than you do?
smile.gif


</div></div>

Absolutely, I want to learn, so educate me on that... you talking 500, 1000, 2000 yards ? you said 5 degrees is a miss, I want to learn more.
 
#294
Re: Spindrift Calculation??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body"> Absolutely, I want to learn, so educate me on that... you talking 500, 1000, 2000 yards ? you said 5 degrees is a miss, I want to learn more. </div></div>

Bloody Hell we're both having a quiet day to carry on like this!

1. Trigger said it not me.
2. I would have thought the answer was bleedin obvious.

smile.gif
 
#296
Re: Spindrift Calculation??

Brown Dog do you even own any rifles? Didnt the gun grabbers take your rights away!!

Wait this is all becoming quite clear now this spin drift data he is posting is for his .22 LR

 
#297
Re: Spindrift Calculation??

Now Nomad, I'm sure he is Top 5 shooter over there... and while I maybe ballistically challenged according to him, who only reads between the lines, I at least get to shoot on a regular basis anytime I want.
smile.gif


One day, I might actually hit something. Then again it has been awhile since I shot a competition myself, although my last two were pretty good. I mean, 4 first round misses out 60 shots, my average isn't that bad for not knowing what the bullet is doing, and the time before the that wasn't awful either.
 
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