Range Report Spin Drift

[Shady_Jay]

Re: Spin Drift

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: The Mechanic</div><div class="ubbcode-body">You must not be very busy Frank. This is the most posting in one thread by you I have ever seen. Usually one post on Coriolis, or spin drift and that's it. But I must say I am enjoying it. Time for a book. If Plaster can do it so can you.
Chapter one. Spin drift, lunar drift, and Coriolis.
Chapter two. Helo shootin' movers.
Chapter three..... </div></div>

He and his boyfriend used to fight over spin drift and they have since broken up. He thinks his ex-BF still lurks and reads his posts so he launches huge tirades of anti-spin drift. Thinking it will all end up like the last scene in Officer and a Gentleman.



.......except it would be two dudes in white uniforms






sharing the same hat

 

[Shady_Jay]

Re: Spin Drift

or helmet?

 

[Lowlight]

Re: Spin Drift

CKA is upset because he dials SD, he heard it was the thing to do and he still can't hit shit.

He also adjusts his belt for midsection drift as it keeps moving farther and farther away from center.

 

[Shady_Jay]

Re: Spin Drift

poor little feller

 

[Lowlight]

Re: Spin Drift

We'll see who is crying when you're banned from my matches for a year. I really think 2012 will be your time to break the top 30.

 

[Shady_Jay]

Re: Spin Drift

Banned again.

 

[deadly0311]

Re: Spin Drift

CKA im gonna have f**king nightmares now. Thanks asshole

 

[sharac]

Re: Spin Drift

One could do experiments with laser pointer (similar to air rifle trainers) mounted to a rifle with built in sensors which would keep track of pressures exerted on the rifle (all directions, bipod loading etc...) and finally laser beam pointing to a sensor @ 1000m to keep track of point movement through entire shooting process. I think results would be surprising to some who believe that an average person can keep all those variables within 5% for an entire process from settling in to trigger break.

Also when reading stories of hits at extreme ranges one can easily add for each success story 10 or more failure ones however those are not good commercials and are usually left untold...

 

[Lowlight]

Re: Spin Drift

I couldn't agree more.

Part of my problem with the people who immediately point to SD is the fact they know nothing about the shooter, his level of skill, or his equipment. They read that the group landed to the right and instantly talk of SD.

The thing with Doppler, Litz, they are using raw data so when something like a ballistic calculator figures a solution it has every piece of data available to figure the "projected" path of the bullet knowing they are not putting the human element into the equation. They know this because they can't so the use what they can. However, clearly, even with the best possible ballistic solution people still miss the target consistently.

You know the range, you used a $3600 PLRF 10, you doped the wind to 1 mph with a Kestral 4500, you have chronographed the loaded with an Oehler 35P, you included up to the minute weather data, yet people still miss the target despite the best information available.

I saw this post this morning and I think it is excellent. Ask yourself if you go to this degree to test your equipment because if you don't and you still feel dialing SD is the answer you don't understand the question completely.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Good words, Jeff. And good tips on measuring scopes. Thanks.

For others asking, I'll try and give a little primer.

First of all, check out Lindy's http://www.arcanamavens.com/LBSFiles/Shooting/Downloads/ScopeChecking/ for some excellent information some of which I'll duplicate below.

It's not rocket science guys, you don't need to be an Engineer or even be particularly smart. You just need to be smart enough to realize it's an important thing to do if you shoot long range much.

About the easiest method in "the real world" is with a yardstick because everybody has one and they work out nicely being exactly 10 Mils at 100 yds:

Naturally it's easier to be more accurate with a higher powered scope:

Easy way to verify the calibration of your reticle. 10 mils, 36". Bam, done.

Next you want to verify click value and/or reticle perpendicularity with respect to the turret movement. For this you need to hold the rifle very steady. It's very difficult to do by yourself by hand; if you do it a bunch of times and sort of take an average you can get an idea if there's a big error but you won't be exact. Having buddies hold the rifle and click the scope while you look increases accuracy somewhat. But by far the best is having a gunsmith vice of some type so you can solidly lock down the rifle.

I've seen people mention using calibrated paper. That's fine too as long as it's big enough (measuring 10" or so at 100 yds just isn't enough accuracy; I feel 10 mils or more is the minimum), it's far enough (the closer the paper or object is the smaller the errors will be that you're trying to measure) and it needs to be far enough you can eliminate parallax <span style="font-weight: bold">completely.</span>

You don't even need any measuring device to get some good data. With a good tactical reticle, you can get a relative measurement between the reticle and the turrets by pointing at anything. Typical Mil reticles are very easy as the top and bottom posts are usually 10 Mils apart. Simply line the top of the bottom post on an aiming point in the distance exactly and crank in 10 mils. If the top post's edge is now exactly where the bottom post's edge was, your reticle matches your clicks.

Relatively speaking they're dead on with one another. You should still check them with a yardstick, barber pole, etc, to make sure they're absolutely correct, but in my experience reticles are more consistent than click values so your odds look good.

The same goes for reticle cant with respect to the turrets. All you need is a straight edge at which to aim. It can be a yardstick, post, corner of a building, etc. But it needs to be perfectly straight.

Lock down the rifle with the reticle on the edge--exactly lined up on the edge and crank in 10 mils or so. If the reticle stays on the edge, you're good. If it moves laterally with your vertical turret input, you have a reticle that's not square with the turrets. Clicking windage to see how many clicks it takes to put the reticle back on the edge will allow you to calculate the angle.

Another tool one can use to check these things is a collimator. Some quality boresighters with a good grid qualify so we aren't talking about some super expensive lab equipment here. If you do things correctly, you will get exactly the same answers using one of these and doing stuff "in the real world." I've done it enough times both ways to feel very confident accurate results can be had using one of these--actually I feel this method provides better accuracy since rifle movement is taken out of the equation, mirage is taken out of the equation, parallax is taken out of the equation, etc.

Here's a visual on how that works:

First, line stuff up and check the reticle against the grid. This grid is in IPHY. As you can see, the 2 mil mark above the horizontal stadia and the 8 mil mark show 10 mils equal 36" on the grid--within a fraction of a line width or so which I figure is "close enough."

Then you line stuff up; I used a line to the right of the main one as it made the pics look less cluttered. For checking reticle cant you must line up the vertical line with the reticle as well as humanly possible.

Crank in 10 Mils. Here are your results. As you can see with this scope, the first thing you've noticed is the reticle is no longer on the line. It has not just shifted a tiny fraction laterally but you can actually see daylight between the line and reticle. This shows the reticle cant with respect to the turrets (the tool and the reticle are lined up making the turrets canted with respect to them).

Measure it numerous times, line the thing up over and over and you get an average of roughly 1.5-2 clicks required to put it back on the line. That translates into a degree or a bit more. Just enough I can't say "good enough."

Next notice the reticle has moved a bit more than 37" where it should have only moved 36". We checked the grid against the reticle so even if the grid was off, that would mean the reticle was also off as the reticle and the turrets don't agree. Either way, you have a problem.

Now while you don't need to calibrate a yardstick, you should calibrate (or at least check the calibration of) your grid in the collimator. The easiest way of doing this is checking it against scopes with known good reticles--that you've carefully checked in the real world and verified. I've done that with this one with numerous high end scopes (including the IORs pictured above but didn't happen to take a pic of them) so I know it's within a fraction of 1% true.

But for peace of mind it's always good to have a control, a standard, a sanity check. For this I threw on a Premier 3-15X50:

10 Mils on the reticle measures 36" within a fraction of a line width ("good enough").

Line things up the same way.

Crank in 10 mils. As you can see, the reticle is still on the line. It may have shifted a small fraction of the line's width amounting to a small fraction of 1 degree, but it's such a tiny amount likely challenging my ability to line them up correctly--definitely falling in the "good enough" category.

Also notice it moved 36", within a fraction of a line width. Notice the 10 Mil mark on the upper vertical stadia is exactly on the zero line indicating the reticle and turrets match exactly.

In other words, it passes as the deviations are so tiny the accuracy of the tool and my methods may be responsible for some or all of the deviations.

Hopefully if anything good comes of this thread it'll be people get educated a bit and measure their optics. I didn't start doing this when I bought the PST and it certainly isn't the first scope to have less than perfect results. The nasty truth is most people who are thinking their scopes are perfect only think that because they have not measured them.

People mention lack of QC.... I'll remind them once again Leupold says +/- 3 full degrees of reticle cant is within spec and will pass the best QC in the world because it's within spec! I measured this one at only around 1 degree.

There are manufacturers selling scopes a shitload more expensive than this one where +/- 2% is within spec for click value. This scope is just a hair outside that mark.

Most people would never notice these deviations. Many people would notice similar deviations on their own favorite scopes of whatever brand if they actually measured them.

So again I'll ask people keep the proper perspective. I get paid to be anal. I make my living worrying about tiny little numbers. It's hard for me to do things any other way--especially when I enjoy being able to make first round hits at crazy ranges with new equipment and new loads, etc.

When you worry about the little things, the big things take care of themselves. So you don't have to blame being way off on the first round on "ballistic programs aren't accurate, they just give you a rough idea," or "the BC of this bullet out of <span style="font-style: italic">my rifle</span> is really 1.5!!!" or "it must be a bunch of spin drift...yeah, that's it!" etc.</div></div>

 

[captrichardson]

Re: Spin Drift

Very interesting discussion, really shows the broad depth of view points within the long range shooting community!


To further some of the earlier posts,

For anyone who would like to learn about Long Range Ballistics, I think this is a must read.

Bryan Litz - Applied Ballistics

IMHO, this is a must read because it is based largely on scientific principles and research, combined with real world experiences. I am not going to say that it is "perfect", but if there are any issues with it, I would guess that they are well beyond the realm of most shooters.

Chapter 6 covers Gyroscopic or "Spin" Drift and Litz covers 2 models/formulas that can be used to predict the drift. He clearly points out that it DOES exist, and provides Doppler Radar Models that document it. He also shows the correlation between the models that he provides and the actual recorded data. Next, he points out that it is something that is very difficult to accurately predict due to a large number of variables. Finally, he makes the point that in some situations that it would be practical to try and account for it, this is especially the case with longer range shots. However he also makes the point that in most situations, other variables will have a greater impact on accuracy, and getting an accurate prediction of the drift can be very difficult, so in many situations it is simply not practical to try and account for it.

The Ballistic Software that he provides with the book, does have the ability to model spin drift, assuming the correct data can be entered into the program.

Per many of the posts above, if you have "Mastered" all of the other elements of Long Range Marksmanship, then Spin Drift might well be one of the final elements to try to incorporate. IMHO, and as others have pointed out, chances are there will be many other factors which will have a much more immediate and significant impact on your shooting.

Best of Luck,
M Richardson

Edited to fix picture.

 

[USFTR]

Re: Spin Drift

"Well I am not going to apologize for anything I said here, I see no reason for it."

This is very unfortunate and perpetuates the negative image this site has on other forums.

"…more people feed into myths and legends and lead people down a false path rather than being honest and telling someone they are screwing up the fundamentals. So if honesty is a problem, then I am guilty. Too often people let others simply shoot, when they are supposed to be instructing and overlook obvious errors in form or execution. I chose to hammer down on shooter, and not focus on what may or may not be issue."

So how can you know the issue without seeing the shooter? This is a problem with diagnosing problems/issues in an online forum. From the original post, he wanted to know if this could be a factor. A more appropriate answer from some members here could have been “yes, it is a factor, but you may want to look at your body position and especially trigger control as a more important factor”. The perception I get from some members (see above) is that you have huge egos and feel superior to everyone else to the point that you are condescending.

"And I think I am bit familiar with F Class, and have shot a match or two here in Raton, so I understand the "target" issue. You're X ring is only one component of the entire target. I can tell you this, I would be willing to go out on a limb here and say you are probably shooting a 8-32X scope, maybe as high as 42X, and that your quartering a very large target hoping to bring them center."

42x Nightforce NP-R1 reticle. No, not quartering a target but pin pointing a specific point on the target to account for wind and elevation changes due to terrain and wind direction/speed. I actually can’t see a large part of the target at 42x, but I can aim very precisely (probably within 1”+/- of a specific point) and see fine details in mirage. So I think my equipment is set up to see this phenomenon fairly well.

"So the idea you are cold shooting a target in F class isn't exactly the same. you get sighters, you get spotters on the target, you have coaches, wind flags and known distances that point to a 4ft number block behind a 6ft square frame."

Yes, we get sighters, but the idea is to be center on the first shot, or at least that is what I’m trying to do. If the wind is dead, then I can account for the drift and I know what my first wind dope needs to be. We do not always have flags and have to rely on mirage, high grass, bushes, etc. No coaching is allowed in individual shooting and the size of the target frame is irrelevant to making a center shot since I’m not seeing the entire target anyways.

"Here, things are slightly different. The reticle covers anything that small especially at 800 yards and beyond."

So you are saying that with your equipment for your style of shooting, you can’t hold precise enough to worry about spin drift. I perfectly understand this. For your style of shooting, 42x is a huge disadvantage for target acquisition. I used to have a scope like this. With my equipment, I’m only covering a very small portion of the target and those small differences matter.

"Granted many are now making cross over scopes and reticles that are somewhat like the NF, very thin, but still, your average tactical scope cannot see a 5" wide target and I am very sure you are not first round hitting center on something that small. Besides you have dope for the yard lines you are shooting. You're going for it sure, but be honest, the 10 ring is nice too. You're not complaining about missing center if you hit a 10. An 8 is disappointing, a 10 is every bit as important as the X."

Good point, but in Fullbore shooting, especially when pair firing or 3 to a mound, there is a distinct advantage to make those first two sighting shots count and rewards those who can dope wind. There were many times in England when I was able to convert my sighters to record shots and finish early because I’m taking ALL factors into account with my first shot. I think it served me well based on the results.

"I have dug up targets and can show you an 800 yard target that started with two rounds on steel where i transitioned to a paper target because someone on here claimed to be shooting a 5" Shoot N C at 800 yards. I wouldn't see the 5" target behind the reticle, but managed the next 3 nicely in the black, and my cold shot and follow up where just slightly left of center when I figured the wind. Adding for drift would have been a miss, plain and simple the calls were well placed from the start. So should you want to see them, I have them available."

That’s all fine, but in this case, as most cases, the wind was a major factor over the spin drift and proves nothing. You are going to have some error in doping the wind that will mask, positive or negative, the drift that is real.

"The entire system plays a part of it... is the scope tracking true, is the shooter simply focusing the parallax knob or actually understand and adjusts for true parallax and not just image focus, this stuff matters much more than adjusting for SD."

I never said that drift was a major factor, but it is one small factor. Learning the wind, correct body position, and trigger control are major factors that a shooter can control and will have a larger factor on their accuracy (assuming equipment is in order).

"yes it exists, yes it has value, but only when all things are perfect."

Good, so we seem to agree on something concrete. The rest is just opinion based on personal experience.

 

[Jeff in TX]

Re: Spin Drift

Frank,

I was really hoping to stay out of this one, but I just can’t resist. If we’re lucky this could turn into another 47 page debate on spin drift like we had a couple of years back.

Folks, Frank has done an excellent job explaining why spin drift is a non-factor. I didn’t say it doesn’t exist as it does.

I’ll take a stab at this which will probably do nothing more but increase a senseless debate.

Does spin drift exist? YES
Can you calculate for spin drift? YES but not consistently or accurately

Even if you calculated correctly for spin drift, any attempt to compensate for it gets lost in wind(s) and into a whole host of other variables.

• In a vacuum you can measure and compensate for spin drift. However we don’t shoot in a vacuum.
• There’s no such thing as a totally windless day
• Winds do not blow at a consistent speed, direction and duration across the range
• Wind speeds and directions can change at different altitudes
• It would take a rifle with .1 moa or less to even attempt to compensate for SD. Anything greater than .1 moa and SD is lost in your accuracy.
• Canting your rifle by 1% will negate any attempts at compensating for SD
• And my list of variables can go on and on

Yes Brad at JBM has come up with a calculation to calculate for SD, but it’s not exact. It may get you close or it could be way off. Bryan Litz understands this well and he and I have debated this in the past.

One thing no one has brought into play and something you’d have a dickens of a time measuring but is a major contributor to accurately measuring SD is how quickly does your bullet stabilize? Meaning, how quickly does the bullets nose stabilize to the on coming airflow. This has a major effect on SD. These also plays into all of the barrel variables such as twist, twist rate, barrel diameter, barrel length, velocity not to mention did your bullet enter into the barrel and lands and grooves straight?

One cross wind or wind velocity change cancels out any SD you might have calculated for. That right there should end the debate. Throw in a long list of shooter variables and it should further cancel out any SD.

Debate all you want but the facts are the facts, any SD gets lost in the wind or shooter variable.

I tell shooters to solve this issue if your bent on compensating for SD is to sight your rifle in .5" left at 100 yards. But then that starts a whole new debate.

 

[Lowlight]

Re: Spin Drift

Jeff (usftr), I guess you never shot with Larry & Co because ego and condescending are most F Class shooter's middle names. Or is that the Palma guys, either way if I cared what people thought of me I would have never joined the USMC or ventured out past the kitchen, so I don't see the issue, nor do I see anything I said as being so negative. I have gone out of my way to provide clear facts into the factors that effect hits on targets. I detailed my thoughts, provided evidence to back up my observations and experience as well, I have canon of experience around different shooters that tells me, 99% of the shooters out there have issues with the fundamentals. You being a member of the F Class team and a world class competitor cannot compare your experience level with the average shooter. You are clearly in the top 1% of your sport. You more than anyone know there is no magic bullet and dialing 1 MOA Left At 1000 is not going to guarantee a hit on any target for anyone. Practice and rounds downrange is the only way to play carnegie hall.

Excuse me if you feel I am wrong, but I personally think it is mistake to think people are up to your standards of shooting and can "see" the difference or the drift that you are experiencing. You're equipment is night and day and purpose build for your game.

You acknowledge the factors I have listed, but continue to dismiss the human factor in all this, as does every piece of information collected does. It is raw unedited and does not take into account the fact people blow shots, the majority of those blown shots are to the right of center. Some how you act as though you never heard of dialing for a poor trigger, or that people have been known to zero their flinch.

Your rifle weighs how much ? You use what kind of rear rest ? Your trigger is set to what weight ?

There is a reason they call F Class "Belly Benchrest" so put in context, you have to realize where you are, and who your audience is. I feel I know my audience, and I know the equipment used, it's my job, so if you call that arrogant well I again stand by my statements and accept that.

Other than the fact you guys, the F Class Team do very well making money off the members here, I really don't understand why you guys come over, you all seem to have a negative opinion of the place as you said more than once. If you think we or me are jerks, why bother ? You've said it several times now, I never attacked you personally but you insist on putting the down the site because we disagree on the merits of adding an moa.

Best of luck to you in your next competition... although don't be surprised if you hear I was rooting for the Brits or Canadians. Besides it will give you guys something to talk about on "other" sites.

 

[Shady_Jay]

Re: Spin Drift

I blame the parents.

 

[USFTR]

Re: Spin Drift

First, leave the Team out of this. I’m speaking for myself and nobody else. I have never put anyone down on this forum. I have seen threads here posted by Hide members from other forums about the Hide. I have never engaged in any form of negative comments about the Hide either here or on another forum. If you feel I have, then please show me. They simply do not exist. I also appreciate the support from the members here and this is why I joined the forum, to give back.

Second, we just see things a little differently. We both agree spin drift exists and we both agree the numbers originally quoted account for more than spin drift. I agree some people may also “zero their flinch” or have poor trigger control (common issue). What offended me personally was the insinuation that everyone that commented that spin drift does occur is just pulling the trigger to the side. I did go back and read every post again from the beginning. The comment did not come from you, so I apologize if you feel I singled you out unfairly. I decided to engage you in conversation because you were the one trying to convince everyone that it was a trigger control issue.

On the technical side of your argument above, I’ve said that I add 0.5 MOA left at 1000 yds in absolutely calm conditions. After reading the posts again, this number is quoted several times by those that seem to have actual data. I agree anything over that is wind or shooter induced. So in the future, I’ll keep my comments and assistance to the other members on the Hide to myself.

 

[Guest]

Re: Spin Drift

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Captain Kick-Ass</div><div class="ubbcode-body">I blame the parents. </div></div>

Interesting,... But I've a new Dove Tail Machine awaiting set up,...

 

[Guest]

Re: Spin Drift

I shoot canted reticles to comp, 300wm 190smk 11.27 twist 0.5 left
.308win 175smk 12 twist, 0.75 Left. All targets I've missed were not from the retical cant, it was me missing the range or wind.

 

[JRose]

Re: Spin Drift

I have my barrels custom straight rifled to eliminate spin drift...

 

[Lowlight]

Re: Spin Drift

Jeff,

Here are the quotes I am referring too:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I am amazed at the attitude of several people on this forum. Obviously there are two camps here with very different opinions. The respect shown for our fellow marksmen and competitors has gone down hill in my opinion</div></div>

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">"Well I am not going to apologize for anything I said here, I see no reason for it."

This is very unfortunate and perpetuates the negative image this site has on other forums.
</div></div>

and especially this one:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">The perception I get from some members (see above) is that you have huge egos and feel superior to everyone else to the point that you are condescending.</div></div>

"see above" - well above this you are talking directly to me.

I see all this as negative and directly engaging me since it was you and I speaking on the subject.

I started out in 2001 and forward shooting several Spirit of America Matches and because of the attitudes of the shooters I encountered, particularly the F Class Team I walked away completely, so I will happily leave the team out of this, but calling me and/or others egotistical and condescending is like the pot calling the kettle black if you ask me.

I have no issue with you personally, but I feel you on more than one instance made the points above directed to me. I get you said it wasn't me you speaking on, but it certain doesn't look that way.

 

[runngun]

Re: Spin Drift

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jeff in TX</div><div class="ubbcode-body">
• In a vacuum you can measure and compensate for spin drift. However we don’t shoot in a vacuum.
</div></div>

There is no spin drift, or any other atmosphere induced drift, in a vacuum.

 

[sinister]

Re: Spin Drift

Drift topics always seem to end with fish-slapping at least once a year.

Drift is a noted component of rifled arms. Naval, artillery, tank, and rifled mortar gunners compensate for the effect every day. It is noted in the ballistic table for each different round.

It does not NORMALLY affect rifle fire at typical ranges -- the effect may be noticeable or negligible.

You can almost time when these threads go to hell. "Yes it does." "No it doesn't."

Worse than a bunch of children.

 

[Graham]

Re: Spin Drift

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sinister</div><div class="ubbcode-body">"Yes it does." "No it doesn't." Worse than a bunch of children.</div></div>No we're not.

 

[ewoaf]

Re: Spin Drift

 

[Alaskaman11]

Re: Spin Drift

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Captain Kick-Ass</div><div class="ubbcode-body">I blame the parents. </div></div>

You know, I love the Capt, he reminds me of a guy I knew in the army. He was the guy that would sture up shit and get fights going. As for Frank, I think I have learned more in 24hrs then in the last 6 months.

 

[Lowlight]

Re: Spin Drift

I understand this has been beaten to death and not just here but basically every time it comes up, but I have a question that really should be addressed to the "rocket science" around this subject.

Currently, thanks to the use of computer modeling, the expanded data provided by Doppler, and the fact ballistic computers are pushing Spin Drift to the forefront of many shooter's minds, why aren't the people and companies who are promoting the correction NOT advocating the use of Left Hand Twist barrels especially in calibers that are designed for engagements beyond 1000m?

If you think about it, the benefits of being able to cancel out effects like coriolis beyond or at least significantly offset the effects, this would be the most logical recommendation for all builds like those chambered in, 338, 375, 408, and .50.

If you consider the questions regarding rifle twists for a 308, 1/12, 1/11, 1/10, etc. It should be the standard practice. However, we don't see any recommendations in this direction. I would think someone like Lapua, who has their own Doppler data and is in the northern hemisphere would be saying very loud, use a left hand twist.

I know Pesja mentions The benefit of a left hand twist in his book on modern ballistics which was written in 1989, so the guys computer modeling have to be able to show the benefits, especially at the further ranges. Over the last few days I watched the ELR bullet train wreck unfold with arguments running up and down the spectrum, but not a word on using a left hand twist. Maybe they are advocating it and I just overlooked it, but it seems to be a missing element in the puzzle.

 

[Lindy]

Re: Spin Drift

Bryan Litz mentions that effect of LH twist barrels in his book as well.

 

[captrichardson]

Re: Spin Drift

Left Hand Twist, very good point!

Have you talked to someone like Dan Lilja, I would guess that he would be a good person to "bounce" that off of?

With the latest round of 1 mile + sniper kills in A-Stan, the increasing popularity of the "ultra long range" calibers, and the growing interest in "ultra long range" shooting, seems like that may well be an issue that could motivate some change?

Amazing how things continue to be done, just because that was the way they were always done!

I remember my days working for Uncle Sam, and I am very glad for the sake of those who are currently serving that many of the "old standards" have finally been broken and things are moving forward in some areas. It is really a shame when civilian shooters have better equipment and training then the military shooters who are relying on that skill to accomplish the mission and stay alive!

Best of Luck,
M Richardson

 

[Guest]

Re: Spin Drift

This is no different than the debate between right an left hand rotation engines. NASCAR runs R/H engines while turning left. Which way does a R/H engine twist in the frame at full throttle? Where is the bulk of the lead they install, when turning left?

Spin Drift is a never ending debate, but we have made head way as now everyone believes/knows SD is a live number. Will it alone cause you a miss at 1K on a MOA target maybe, maybe not. My guess would be not, IF you have everything else in your house in order. Can using it improve a bench only shooter, I'd guess no if he gets sighters.

I'd pass on the SD number, to know more about how to close the distance where SD won't make any difference, in a Tactical setting. You always hear about that one long range shot that makes headlines. The meat of the task is much closer where SD means shit.

 

[Tactical]

Re: Spin Drift

Wow, Spin Drift again.

I shoot F TR as does Jeff. Jeff is one hell of a shot and a Scientist so these types of things bug him. He talks like a scientist. We roomed at Worlds for a couple of weeks and he made my head hurt. LOL. The F TR guys shoot off a bipod with rifles that weigh about same as anyother sniper type rifle. Heck I competed for awhile with GAP M40A3 and did OK.

Frank is a field shooter so he wants energy on target and does not care about what gets lost in the crap we can not see in field anyway. Different folks different needs. You should have seen his face when he heard how I threw powder and bullets in a case and fired them. Most F Guys spend so much time with ammo they should name it but I know I am going to mess up a wind call worse than my ammo will shoot. I dont worry about it and dont want to know I needed to neck turn, neck size only or what else I am doing wrong. It would bug me LOL I just weigh a charge very well, drop i Lapua case, seat a Lapua bullet and shoot. Works OK so far.

I come from the door kicker side and started F TR because I am broken. I like it alot. Just pure me versus the enviornment with a crummy 308. Rules are simple and the same match to match. How I do in the match is secondary. All about me versus ellements.

Spin Drift does exist but from best I can figure and calculate from books and books of shooting its about .5-1 moa for 1000 yards. On steel thats hard to hold within .5 moa of perfect center anyway. On X Ring of 5 " with 42X its easier. When I shoot F TR if I see wind left to right I do best guess and add .50 moa for drift. Then correct for F Up. Once basic wind zero is established I just hold left or right as wind changes.

The F TR Team is not the Open Team. We are not Belly BR guys, most have tactical backgrounds. Neither F TR or F Open are stuck up bunches and several come to SH regularly. Individuals are not the teams. Some good some bad just like here. Just like everywhere. They can all shoot very well or they would not be on either team. Well except me I got lucky.

 

[sinister]

Re: Spin Drift

Go for a left twist and you'll have left drift. You'll also have opposite torque while the bullet is in internal ballistics phase. Most shooters are right-handed.

 

[Lowlight]

Re: Spin Drift

FYI, I met with guys today here in CO who are using LH Twist 6mm barrels from Rocky Mountain Rifle works to great effect... I pick up a BigHorn Arms Action in an AICS with a Mark Chanlynn barrel on it. It was explained he is using Left hand twist and Ray Dog from TBAC said it shoots lights out.

In ELR if a LH Twist will cancel coriolis you have a win, win... as stated it is mentioned, in the books on ballistics but glossed over.

 

[krw]

Re: Spin Drift

Let me clarify a point, I don't get paid to take the shot. I raise cattle and chickens and have a thing for highend rifles and optics and love to shoot. Hypothetically here in Arkansas if you shoot in a true North direction, with a constant W-E wind at 15mph, RH twist bbl. After you get rifle dialed in, you swap ends. Now your shooting South, still a W-E wind. Spin drift should change as should the coriolis effect. The range was 1200yds. Would this not have a drastic change on the ballistics of the bullet from the zero you had before you changed direction? Also if someone could explain, wouldn't a LH twist rifle barrel really help in one direction but not in the other like I think a RH rifling would?

 

[sharac]

Re: Spin Drift

Much of it is also pure commercial bullshit. One million gizmos to launch a bullet, one million gizmos to buy, one million gizmos to blame for a miss. A mirror is a costly affair it can severely diminish ones ego...(that's why they don't sell as well as neck turners, bubbles etc... to shooting crowds - worldwide).

In chasing groups some have forgotten the purpose of the rifle and while i'm not bothered by it (science of shooting, ballistics, striving for oneholers @ 1000m) i am bothered by exploitation of it for commercial purposes and taking spotlight away from what matters the most - shooters skill. Some people really expect (check out how many questions for people who started shooting are such) that they need to shell out couple of thousands dollars to get .25moa rifle, several other "helper" items and surprise surprise can't hit a barn - must be the spin drift, coriolis or sudden gust of minitornado...


PS: I don't think training camps/events also (compared to buying stuff) are a magical remedy. Basics CAN and SHOULD be learned before even buying anything larger than a BB gun and after that is drilled into ones head

then you if you still feel the need go train, get advice and buy that latest moon gravity compensator...

 

[hexades1]

Re: Spin Drift

Glenn D. Zediker has a book called Competition Handloading - making the target bigger. I think that title pretty much summarizes it all when shooting long range. Do everything to decrease your groups and to help you place them on the intended target. SD is just one of them (Zediker does not talk about it at all). It and coriolis effect are just icing on the cake. But you should utilize them to shoot better.

Shoot what and how you want there is always someboy shooting better somewhere. I do not see why I should not take all the easy steps to help me shoot better.

 

[sharac]

Re: Spin Drift

I think the point was: There are other things which influence your shots MORE than SD and you should be working MORE on those things. Yeah if you are really consistent, happy and can judge wind within 5% of actual speed then go and incorporate SD, Coriolis and any other variable you like however i'm pretty sure there are very very few people here capable/trained to be that good.

Imagine a person coming to the line with a laptop, does the math for 10 minutes, calculates every ballistic parameter/variable there is, gets all comfy lines his sights uses several bubbles/cosines gets his .338lm superstable puts finger on the trigger and kabaam...miss...WTF!!! how can that be....if he was recording himself he'd see that just before squeezing he tucked his head and closed his eyes as magnum started doing it's thing in the wrong direction...
Its just an example (i've seen it and not even with .338lm) but there are many like it. I for myself know that it will take quite some time before i will bother myself with SD or Coriolis or humidity as i'm lacking quite a bit in several other departments. When i shoot at a distance i remember load/settings and try to mimic those incorporating changes (wind) and going from there. I'm nowhere near to the point i can say okie, temp&humidity add .3moa, wind 3moa left, coriolis .2moa, SD .4moa, shooting angle deduct .4moa and kabaam 1st round hit at a 1km mark (and not being a barn) (highly doubt there are many people that can do that naturally) what i get is first round hit (most of the time but still get flukes like last saturday at 700m couldn't hit paper 1mx1m as load appeared to keyhole -weird a first for me) on 1mx1m paper and go from there...