Help Needed with LB3.0 and .338 Bergers

[bigngreen]

OK, so I'm trying to get my mind around Coriolis so I layed out 4 tracks in LB desktop and then changed the Azimuth to 0*,90*,180*and 270* since LBD does not stack the corrections you can look at Coriolis X and Coriolis Y. Coriolis X has the same value in each track and they are positive numbers and Coriolis Y has 0 value in 0* and 180* but has a positive value for 90* and a negative value for 270*. I can see why it is such a compicated thing to deal with because there can be so many combo's of X and Y value in an entire 360*.

Can someone put what that is saying into english for me. Please


OK, so I re read your last post Phorwath, I guess it took a couple more tries at reading it, I think I get it. I was getting messed up by Coriolis X all being the same value, I understood the Y axis cause your shooting into or away from the rotation of the earth and in effect lengthening or shortening flight time. So all shot directions will curve to the right but the closer you get to east and west you will also have a higher or lower POI.

 

[Pdvdh]

OK, so I'm trying to get my mind around Coriolis so I layed out 4 tracks in LB desktop and then changed the Azimuth to 0*,90*,180*and 270* since LBD does not stack the corrections you can look at Coriolis X and Coriolis Y. Coriolis X has the same value in each track and they are positive numbers and Coriolis Y has 0 value in 0* and 180* but has a positive value for 90* and a negative value for 270*. I can see why it is such a complicated thing to deal with because there can be so many combo's of X and Y value in an entire 360*.

Can someone put what that is saying into English for me. Please

Well you threw me for a loop there for a second. It's a matter of interpretation of the X & Y identifiers. X refers to horizontal. Y refers to vertical.

The fact that Coriolis X values are all identical values with the four different azimuths means that horizontal drift is equal in all directions, and the positive value indicates a rightward drift.

Coriolis Y values of zero (0) for the 0* and 180* azimuths (directions of fire) means that there is no vertical component of drift (rise or fall) when shooting due north (0* azimuth) or due south (180* azimuth).

The positive value for Coriolis Y with the 90* direction of fire (due east) is identifying an upward drift - the bullet will strike that quantity/value higher than it would otherwise impact without Coriolis affect.

The negative value for Coriolis Y with the 270* direction of fire (due west) is identifying a downward drift - the bullet will strike that quantity/value lower than it would otherwise impact if there were no Coriolis affect.

Same thing I stated earlier but in the LB3 use of acronyms. Horizontal Coriolis drift is exactly the same quantity/value no matter which direction of fire (* azimuth), provided you fire from the same Latitude on the surface of the Earth. The quantity of horizontal Coriolis drift is strictly a function of the Latitude value input into LB3. For me it's 59 - 64 degrees North Latitude, depending on which hunt I'm on in the State of Alaska. The closer to the North Pole, the higher the Coriolis-caused horizontal drift. The closer to the equator, the less the Coriolis-caused horizontal drift.

Vertical Coriolis drift (rise or fall) is dependent on direction of fire. There is no vertical (Coriolis Y) drift when shooting due north or due south. Shoot any other direction and there is some vertical Coriolis drift. The maximum vertical drift is experienced shooting due east and due west. Shoot due east (90* azimuth) and the bullet will experience maximum vertical drift/rise (positive LB3 Coriolis Y value). Shoot due west (270* azimuth) and the bullet will experience maximum vertical drift/drop (negative LB3 Coriolis Y value).

Nuttin to it!

Now the really confusing part is that the corrections in MOA or Clicks is contrary to rise and fall. If the bullet is rising with a due east shot, the elevation dope up is reduced - because the bullet would otherwise hit higher than expected or intended, if Coriolis were not drifting the bullet trajectory upward. And on a due west shot, the elevation dope up is increased - because the bullet would otherwise hit lower than expected or intended, if Coriolis were not drifting bullet trajectory downward.

I researched this to death in 2008.

 

[Pdvdh]

OK, so I re read your last post Phorwath, I guess it took a couple more tries at reading it, I think I get it. I was getting messed up by Coriolis X all being the same value, I understood the Y axis cause your shooting into or away from the rotation of the earth and in effect lengthening or shortening flight time. So all shot directions will curve to the right but the closer you get to east and west you will also have a higher or lower POI.

Bingo! I think you've got it. The LB3 acronyms are part of the learning curve also.

 

[Broz]

Vertical Coriolis drift (rise or fall) is dependent on direction of fire. There is no vertical (Coriolis Y) drift when shooting due north or due south. Shoot any other direction and there is some vertical Coriolis drift. The maximum vertical drift is experienced shooting due east and due west. Shoot due east (90* azimuth) and the bullet will experience maximum vertical drift/rise (positive LB3 Coriolis Y value). Shoot due west (270* azimuth) and the bullet will experience maximum vertical drift/drop (negative LB3 Coriolis Y value).

Nuttin to it!

Now the really confusing part is that the corrections in MOA or Clicks is contrary to rise and fall. If the bullet is rising with a due east shot, the elevation dope up is reduced - because the bullet would otherwise hit higher than expected or intended, if Coriolis were not drifting the bullet trajectory upward. And on a due west shot, the elevation dope up is increased - because the bullet would otherwise hit lower than expected or intended, if Coriolis were not drifting bullet trajectory downward.

I researched this to death in 2008.

OK, has anyone ever acually went out and shot a group at 1000 yards due east, then turned and shot a group due west and compared the differences in elevation of Point of impact ? Not talking numbers , research, books and authors here. But actually tested this to varify? If so I would like to hear this from first hand experiences. Please.

Jeff

 

[Broz]

Holy cow, I asked that last question and then recalled my two longets shots on game.

Whitetail doe, kansas, straight West just after sunset, 1137 yards.

The last Bull I took, evening straight East, 1130 yards.

Light wind corrections for both, both with 300 SMK's at 2805 mv. Exbal, No coriolis, or spin drift corrections. Both DRT, cold bore, one shot kills.

I will admit, I was off about 6" windage on each. Both were off the 6" in the direction the wind was blowing.

You can show me on paper how my rifle is off. But, to convince me , either I or you will have to show me in the field with actual shots.

Respectfully,

Jeff

 

[Pdvdh]

Jeff,

I don't have an interest in convincing you Jeff. Trust me. I have no such inclination. The information I'm providing on Coriolis drift - I believe to be factually and scientifically valid. I'd bet my life savings that if we collected the best and brightest scientists from across the world, their testimony would make me the winner. But what you or any other member does with this information - I won't be offended either way.

Personally, I accept Coriolis just as completely as I accept gravity. The mechanism for its cause is completely understood and scientifically proven. It's affect on projectile travel has been accepted as a fact of life by every advanced military in the world for decades. Our military and every advanced military in the world factors Coriolis drift into every long range artillery computer-programmed firing. The farther the projectile travels the farther the projectile will miss the intended target if Coriolis drift is neglected.

I have no goal to be a smarty pants either. Well... I admit I can get that way, but generally only after coming to the conclusion that someone's sniping or headhunting with no valid cause.

Understand that the Coriolis-caused vertical drift is a much lesser value than the horizontal drift. Go ahead and experiment with LB and it will become apparent that the vertical component of Coriolis drift is only (don't hold me to these exact ratios) 1/4 to 1/3 of the horizontal drift at your Latitude. So the vertical Coriolis drift is much less apt to cause a long range miss in and of itself than the left to right, horizontal Coriolis drift. The vertical component of Coriolis drift is small enough that it might be difficult to visually observe and document - even by a good shooter with good equipment at the extended 1300 yard ranges you're targeting. The horizontal Coriolis drift should be easier to document on target, and a comprehensive effort by a good shot with properly tuned equipment and technique (no rifle cant or scope misalignment), under favorable conditions (no cross winds to contend with) should, I believe, be able to document this drift. Try it. Don't worry about obtaining 1/2 moa groups. Zero your rifle dead on in windless conditions at say - 200 yds. Then find the biggest piece of cardboard target you can set up and still hit at the farthest range possible with your bullet still fully stable and supersonic. Aim dead on left-right with only holdover to engage the distant target. Tell us if you experience any rightward POI. The farther the better. Don't worry about the group size. Just look for the center of grouping at maybe 1800 yds. It will be to the right, or else you've got something in the setup of your equipment, a cant, or a crosswind that is negating or counteracting rightward Coriolis drift. I wasn't even looking for it at 1000 yds, but there was no denying I had a left to right drift problem. I asked questions. Got a variety of advice. I researched the science. I corrected some faulty equipment alignment issues. And when I sorted out the cause and effects, the extent of my rightward drift fell right in line with the combined predicted Coriolis and spin drift.

Those pesky modified elevation dope values that you observed while turning LB Coriolis off and on? Those are real whether you believe or don't.

Since I absolutely know that Coriolis affects bullet flight in a predictable and readily modeled fashion, I choose to include that dope in any longer shots that I attempt. I do have my own recommendation on the matter for anyone else trying to kill game or hit targets at long range. But that's all it is - my recommendation.

I have absolutely no hard feelings and absolutely no personal ambitions to force these proven facts on you or any other Forum member. On the other hand, if someone asks, I'm also content to share credible information as I have in this Thread. Any member that wants to research Coriolis drift will come to understand it's not an old wives' tale or mythology. It's been a proven fact for decades and completely respected by every advance military unit capable of launching any projectile long distances. I'm not ex-military, but I would bet that sniper's are at least made aware of Coriolis drift. And that the ultra long range sniper specialist include corrective Coriolis drift dope.

So I'm doped out on Coriolis, and every other reader should be by now also.
gun) gun)

 

[Eaglet]

Jeff,

I don't have an interest in convincing you Jeff. Trust me. I have no such inclination. The information I'm providing on Coriolis drift - I believe to be factually and scientifically valid. I'd bet my life savings that if we collected the best and brightest scientists from across the world, their testimony would make me the winner. But what you or any other member does with this information - I won't be offended either way.

Personally, I accept Coriolis just as completely as I accept gravity. The mechanism for its cause is completely understood and scientifically proven. It's affect on projectile travel has been accepted as a fact of life by every advanced military in the world for decades. Our military and every advanced military in the world factors Coriolis drift into every long range artillery computer-programmed firing. The farther the projectile travels the farther the projectile will miss the intended target if Coriolis drift is neglected.

I have no goal to be a smarty pants either. Well... I admit I can get that way, but generally only after coming to the conclusion that someone's sniping or headhunting with no valid cause.

Understand that the Coriolis-caused vertical drift is a much lesser value than the horizontal drift. Go ahead and experiment with LB and it will become apparent that the vertical component of Coriolis drift is only (don't hold me to these exact ratios) 1/4 to 1/3 of the horizontal drift at your Latitude. So the vertical Coriolis drift is much less apt to cause a long range miss in and of itself than the left to right, horizontal Coriolis drift. The vertical component of Coriolis drift is small enough that it might be difficult to visually observe and document - even by a good shooter with good equipment at the extended 1300 yard ranges you're targeting. The horizontal Coriolis drift should be easier to document on target, and a comprehensive effort by a good shot with properly tuned equipment and technique (no rifle cant or scope misalignment), under favorable conditions (no cross winds to contend with) should, I believe, be able to document this drift. Try it. Don't worry about obtaining 1/2 moa groups. Zero your rifle dead on in windless conditions at say - 200 yds. Then find the biggest piece of cardboard target you can set up and still hit at the farthest range possible with your bullet still fully stable and supersonic. Aim dead on left-right with only holdover to engage the distant target. Tell us if you experience any rightward POI. The farther the better. Don't worry about the group size. Just look for the center of grouping at maybe 1800 yds. It will be to the right, or else you've got something in the setup of your equipment, a cant, or a crosswind that is negating or counteracting rightward Coriolis drift. I wasn't even looking for it at 1000 yds, but there was no denying I had a left to right drift problem. I asked questions. Got a variety of advice. I researched the science. I corrected some faulty equipment alignment issues. And when I sorted out the cause and effects, the extent of my rightward drift fell right in line with the combined predicted Coriolis and spin drift.

Those pesky modified elevation dope values that you observed while turning LB Coriolis off and on? Those are real whether you believe or don't.

Since I absolutely know that Coriolis affects bullet flight in a predictable and readily modeled fashion, I choose to include that dope in any longer shots that I attempt. I do have my own recommendation on the matter for anyone else trying to kill game or hit targets at long range. But that's all it is - my recommendation.

I have absolutely no hard feelings and absolutely no personal ambitions to force these proven facts on you or any other Forum member. On the other hand, if someone asks, I'm also content to share credible information as I have in this Thread. Any member that wants to research Coriolis drift will come to understand it's not an old wives' tale or mythology. It's been a proven fact for decades and completely respected by every advance military unit capable of launching any projectile long distances. I'm not ex-military, but I would bet that sniper's are at least made aware of Coriolis drift. And that the ultra long range sniper specialist include corrective Coriolis drift dope.

So I'm doped out on Coriolis, and every other reader should be by now also.
gun) gun)

Good Post!

Good things to remember for anyone interested. Not to be repetitive, just clinching the nail!

Coriolis Effects

You need to adjust for X (horizontal component) and y (vertical component).

These components take their values due to the earth rotation based on your location (Latitude) and the direction you're shooting (Azimuth).

Your horizontal component is not affected by the direction you're shooting; it's affected by your location (Azimuth). At the poles you get max. values and zero at the equator.

Your vertical component is affected by the direction you shoot as well as where you are located on the earth. If your direction is due north or due south, there would be zero vertical deflection. You hit high when shooting towards the East and you'll hit low when shooting towards the West. Vertical component will be at its max. when you're at the equator and at the poles it goes to zero.

Spin Drift

Has nothing to do with the earth rotation. It's your bullet mass, interacting with the atmosphere conditions; right spinning or left spinning and how fast.
***********************************************

It gets a bit more complicated that that's all I need to know for now!

 

[bigngreen]

OK, I had a light bulb come on lightbulb. One is Coriolis is a fact because the earth is moving while you bullet is on it's way. I like Broz idea of shooting groups in certain direction to see this drift, I can not because I don't have a rifle that will hold a small enough group to give us the resolution it would take. Hopefully the barrel I'm picking up next week will fix that, any way.
Second, the reason some might not see the affects of Coriolis and spin drift is the distance that we sight in at, if you and your gun can shoot small enough groups and you sight in at say 600yrds and you don't allow for Coriolis and Spin drift you have taken them into account during sight in. So you would have to shoot way out there to see it come back into play again.
I haven't had time to play with the number to see at what range you would start to take these into account at sight in.
I have had a problem of all ways being to the right on my shots I miss, I thought this was only due to a bad wind dope, I think I was stacking Coriolis, spin, and bad wind meter. All my missed shot were shot in the same direction with the same wind direction, I was just doubling the wind value to be on target but I bet a lot of dollar if I would have been using Coriolis and spin drift and a quality wind meter I would have been dead on!!!

I have to get my gun back together to test this

The answers a coming to me now, BIG thanks to Phorwath and Eaglet!!!!!!!!

 

[Broz]

BnG, you may be on to something. I have seen rifles that I would say were definatly affected by spin drift. Most, maybe .75 moa at 1000. I could probably say that the deer I shot at 1137 there could have been SD, and that could account for the 6" off point of aim. Also , this was direction of the wind so .... who knows? But the bull at 1130 the 6" off point of aim as left, also the direction of the wind. Good thing I didnt add more left for SD on that shot.

That said, I have my rifle zeroed at 300. This is where I set up the base to be zeroed at when at the bottom of the elevation adjustment. Zeroed I am about 1.5 moa off bottom. This give me the full 63.5 left of the total 65 moa all in up elevation. Just in case I ever want to shoot a mile.

So, maybe my 300 yard zero has taken care of some of these drifts,if so, great!

I really need more time in the field with the Bergers, but so far it feels to me like they have less drift. Is this possible, can one bullet have more drift than another? I am saying that based on the 20 or so shots that I feel were successful at distances from 700 to 1400 where I didnt adjust windage for SD or coriolis. I also feel I need to shoot more to say for sure. I will, and come time to fill a tag I will have my mind set for what I need to do.

Jeff

 

[bigngreen]

Broz, I don't think it would be a good thing to partially compensate for coriolis and spin, the reason being that at some range you will go beyond what you have compensated for. But then if you start using Coriolis and spin in Loadbase it will be off because you have partially compensated for it in your sight in so the accuracy of the predicted trajectory would be compromised.

I think a guy might want to really dig into this, the two shots you talked about are perfect examples of what I've seen and done. The one shot that was left in the direction of the wind, if you were also experiencing spin and coriolis would mean that you over doped the wind. For the most accurate wind dope we would have to know what coriolis and spin was doing because those, I think get lost in the wind dope and we end up saying there was no wind when actually somewhere in the bullet path there was but coriolis and spin took care of it, or we say there was more wind than we doped but in fact it is spin and coriolis stacking, or we say we got a bad range from our range finder because we hit a little high or low.
Granted in a hunting situation very few of us are shooting far enough to see these come into play in a big way.
So knowing coriolis and spin drift does matter in relation to how good our wind dope at these longer ranges using a program to calculate our dope.

I maybe over thinking this but I don't think so.

 

[jmden]

Hmm...I was wondering as well if you zero at 300 yd vs. 100 yd, for instance, that you may not notice as much the spin drift to the right (if RH spin, which is typical) and right coriolis 'drift' (if you are in the northern hemishpere) at longer distances since some of the effects are taken into account with a longer zero, such as a 300 yd. zero.

Some on this board will zero a half MOA to the left to try and take into account right coriolis 'drift' (if in N hemis) and/or spin drift. Litz mentions in his book that a person might order a left hand twist barrel to try and offset the right coriolis 'drift' against the left spin drift, but cautions that later that "spin drift is about 5 times greater than coriolis".

Personally, I zero at 100 yd to have more confidence in shot placement for that quick close shot, if need be, and this has helped me harvest a couple of animals at close range.

I also follow to the 'T' (same tools and all) the scope/rifle setup procedures phorwath mentions earlier, which I think is quite important for the lr shooter to do or the ballistics programs don't seem to me like they are going to work very well. That said, with the little lr shooting I get to do, I'm can't say for sure that I see spin drift (Litz calls it Gyroscopic Drift) and coriolis I see on the targets. Probably just my lack of experience/skill as they certainly exist.

You guys with LB--what does it show in regards to gyroscopic drift...do you see a change in this value with a change in bullet? Say you went from shooting a 300RUM with 240 SMKs at 2920fps to shooting 210 Bergers 2990fps. How does this value change at 1000yds with a 100yd zero...and a 300yd zero?

 

[Broz]

Well I have a set of numbers that I like in LB3.0. Best ones I have entered so far and with applying SD and Coriolis they are very very close to actual shots I have taken (as far as ups are concerned) the recent four I posted, and a few more I have documented. The MV is very close to what I feel is real, the BC is Bryans latest G7 and the DC is well with in Eaglets advice on the DC perimeters. I have 10 rounds left before I have to load another 100. The plan is to shoot these this weekend in good conditions (weather (wind) permitting) and see how I do. I will record azmuth, latitude, and FC for each shot and the error between point of aim and point of impact. I will try work in what I feel is my effective range of 1400. But hope to also send a couple to 1500 or so.

Then I will report here my true findings.

Eaglet, Phorwath, I ask for you two to lock up you guns and ammo and Please, don't shoot the mesanger..

Jeff gun)gun)

 

[bigngreen]

Broz, did you see if there is any Coriolis and spin drift that you need to take out of your 300yrd zero? I'm away from Loadbase so I can't check what there may be, but I think 300yrds with what I looked at last night I would have about .2 of coriolis and spin at 300yrds. That could be a factor at longer ranges.
If you sync your desktop to your PPC then the track you saved on the PPC will be availiable on the desktop and in Results 1 you can see what value X and Y coriolis is coming into play.

 

[Pdvdh]

I promise... fingers crossed...

Spin drift is harder to model than Coriolis. But spin drift will probably cause more right-ward drift than Coriolis. Spin drift is more bullet shape, rate of twist, and velocity dependent, to my understanding.

Place some extra backstop material off to the right hand side so you can catch the impacts from those Coriolis and spin drifted hits!