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Help me out here. In every description of the various versions of ladder and OCW load development methods I have seen, conventional wisdom says to ignore any horizontal distribution and attribute it to wind. We all know barrels oscillate upon firing but what law of physics makes them only oscillate in the vertical axis? Why don't they oscillate in the horizontal axis too? Or in a combination of vertical and horizontal axis? And, if that is the case, why are we ignoring the horizontal dispersion in ladder and OCW type load development?

Thanks,

John


If my people, who are called by my name, will humble themselves and pray and seek my face and turn from their wicked ways, then I will hear from heaven, and I will forgive their sin and will heal their land. 2 Chronicles 7:14
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That's a good question. It would be hard to ignore much horizontal on a calm day. I've heard the same...let's see if anybody has anything on this.

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Been saying this for years personally...

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Originally Posted by TXRam
Been saying this for years personally...


Since you are glued to the hunnert' yard line, you can ignore both smile


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Ok, mr sniper...

And it's 50, not 100...

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When you are shooting a long range 600 yard Audette, there are slight changes in wind between shots that may cause some horizontal. You pick the loads in the node based on vertical

Then generally all of the loads in the node are tested to determine which one shoots best. If there is horizontal at 100, there's something wrong


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Originally Posted by rcamuglia
When you are shooting a long range 600 yard Audette, there are slight changes in wind between shots that may cause some horizontal.


Agreed, but is horizontal never caused by barrel harmonics?

Originally Posted by rcamuglia
You pick the loads in the node based on vertical


Why only vertical?

John


If my people, who are called by my name, will humble themselves and pray and seek my face and turn from their wicked ways, then I will hear from heaven, and I will forgive their sin and will heal their land. 2 Chronicles 7:14
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Originally Posted by Hondo64d


Why only vertical?

John


Because inconsistencies in ignition and wide velocity spreads will result in vertical dispersion at real distance.

that's what's been explained to me. I'm sure Rick will correct me if mistaken. I'm not a match shooter. smile




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Originally Posted by BobinNH
Originally Posted by Hondo64d


Why only vertical?

John


Because inconsistencies in ignition and wide velocity spreads will result in vertical dispersion at real distance.

that's what's been explained to me. I'm sure Rick will correct me if mistaken. I'm not a match shooter. smile


We can also determine that with a chronograph.

My point being that if it's calm (min or no wind), any large spread in horizontal should not be ignored. If it can reasonably be explained by wind, no problem.

I've seen folks just use the vertical with no regard for 4" spread at 300yds on a calm day - I don't buy ignoring that.


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I also don't recall the OCW method ignoring horizontal. It's more about how insensitive group size and group center are to perturbations in charge weight.

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Originally Posted by TXRam


We can also determine that with a chronograph.





Sure you can. But i would think you'd want to see it on a target as well.




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Originally Posted by BobinNH
Originally Posted by TXRam


We can also determine that with a chronograph.





Sure you can. But i would think you'd want to see it on a target as well.


You can have decent groups at 300yds that have wider velocity swings than I'd choose for my loads. I prefer a chronograph for many reasons.

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Originally Posted by BobinNH
Originally Posted by Hondo64d


Why only vertical?

John


Because inconsistencies in ignition and wide velocity spreads will result in vertical dispersion at real distance.

that's what's been explained to me. I'm sure Rick will correct me if mistaken. I'm not a match shooter. smile



Velocity spreads can cause vertical because of the position of the muzzle at bullet exit. No matter how carefully one loads his ammo, there will ALWAYS be velocity differences between shots. Therefore, finding the optimal bullet exit time will reduce vertical stringing.

This is the entire reason The Audette Method trumps all other methods.


Originally Posted by TXRam
Originally Posted by BobinNH
Originally Posted by Hondo64d


Why only vertical?

John


Because inconsistencies in ignition and wide velocity spreads will result in vertical dispersion at real distance.

that's what's been explained to me. I'm sure Rick will correct me if mistaken. I'm not a match shooter. smile


We can also determine that with a chronograph.

My point being that if it's calm (min or no wind), any large spread in horizontal should not be ignored. If it can reasonably be explained by wind, no problem.

I've seen folks just use the vertical with no regard for 4" spread at 300yds on a calm day - I don't buy ignoring that.




Using chronograph data to choose a load will not always yield the best long range load, so that statement is incorrect.

Take a "fantasy" load that always shoots at 3000 fps. Simply because it performs the best statistically, doesn't mean it will shoot the best on paper. The exit time of the bullet could be when the barrel is moving inconsistently causing poor accuracy and vertical.




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Yes, someone that gets it. I always go with best paper results, rather than best chrono results.

Chrono has its uses. But not for load selection.


We can keep Larry Root and all his idiotic blabber and user names on here, but we can't get Ralph back..... Whiskey Tango Foxtrot, over....
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Originally Posted by rost495
Yes, someone that gets it. I always go with best paper results, rather than best chrono results.

Chrono has its uses. But not for load selection.


I don't know squat about this ladder stuff, but I can't imagine working up loads without a chrono.


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I only use one to check to see if the component combination is giving me the velocity I want.


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I only use one to check to see if the component combination is giving me the velocity I want.


I'm not that sophisticated. I chronograph so I can read about it later. Of course I have little man syndrome so I go for the highest velocity I can get that give the accuracy I desire.


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Originally Posted by TXRam
Originally Posted by BobinNH
Originally Posted by TXRam


We can also determine that with a chronograph.





Sure you can. But i would think you'd want to see it on a target as well.


You can have decent groups at 300yds that have wider velocity swings than I'd choose for my loads. I prefer a chronograph for many reasons.


That's maybe because 300 yards isn't "long range".

No one said they don't use a chronograph. use one all the time and have been since the first one's became available. Don't you do more than one thing when you work up a load, like shoot it at distances? As in:
1) chronograph
2) shoot at distance?

What is so hard to understand?


Last edited by BobinNH; 02/04/16.



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Originally Posted by rcamuglia
I only use one to check to see if the component combination is giving me the velocity I want.


Yes, and obviously pressures tag right along with velocity.


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Originally Posted by BobinNH
Originally Posted by TXRam


We can also determine that with a chronograph.





Sure you can. But i would think you'd want to see it on a target as well.


Even more so.


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Originally Posted by rcamuglia
Using chronograph data to choose a load will not always yield the best long range load....Simply because it performs the best statistically, doesn't mean it will shoot the best on paper.


True. Has happened to me mostly with Imr 4064 in several cartridges.


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GD, no one ever said they use a chronograph to determine the load, just that it is better at determining load-to-load velocity differences. Never had a piece of paper tell me the velocity of my load.

Point was the ladder/OCD are NOT for determining velocity differences, they are for determining nodes of your rifle barrel vibration/oscillation. And they don't just move up and down... So you can't "ignore" horizontal dispersion.

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Originally Posted by Hondo64d

Agreed, but is horizontal never caused by barrel harmonics?


I always thought barrels (free floated mind you) vibrate in a figure-8 pattern. Can't seem to find that article.

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Originally Posted by JGRaider
Originally Posted by rost495
Yes, someone that gets it. I always go with best paper results, rather than best chrono results.

Chrono has its uses. But not for load selection.


I don't know squat about this ladder stuff, but I can't imagine working up loads without a chrono.


I don't think he's saying he works up loads without a chrono.

Just that he doesn't pick the most accurate load based on chrono results.



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Originally Posted by smokepole
Originally Posted by JGRaider
Originally Posted by rost495
Yes, someone that gets it. I always go with best paper results, rather than best chrono results.

Chrono has its uses. But not for load selection.


I don't know squat about this ladder stuff, but I can't imagine working up loads without a chrono.


I don't think he's saying he works up loads without a chrono.

Just that he doesn't pick the most accurate load based on chrono results.



I can't remember the last time I used a chrono during load development.

I usually only use one if I'm working with unknown powders with no data, just to see if they will give me the velocity I want.

Determining the velocity is pretty simple when using a Ballistic program at the range. If I'm shooting a 600 yard ladder, I look at velocity data for other powders I feel are close and dial to 600 accordingly. Adjustments are made and noted to the program's velocity figure until the amount dialed corresponds with velocity. After the ladder is done and I've finished the load, I know an estimated velocity. I then shoot steel at different distances up to 1 mile, adjust velocity in the program to give the actual data dialed...

Done.


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Ric and I have already had this conversation.... but I'll submit it to the group:

If ladders "are for determining nodes of your rifle barrel vibration/oscillation"...... How come ALL my rifles are equally as accurate with the 14oz, 9" long, suppressor attached as they are without it? Admittedly, it is always to a lower POI... but the accuracy has never decreased when the can is attached.

Shouldn't the addition of all that weight/length on the end of the pipe do some wonky stuff to my osculation patterns?

Just wondering.... because I think there's a different explanation to why the ladder developed loads seem to be more stable. I'm not nearly smart enough to figure out what it is... but I'm not buying the "osculation theory" entirely.


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Might be an interesting test to do, but I already know the answer.

Try hanging a weight off of your barrel and shooting groups to compare accuracy.

Anyone who shoots any precision type stuff knows that if you stick your barrel through a port on a barricade and rest the barrel instead of the stock on something, accuracy and point of impact goes to chit.

I know first hand that using the Magnetospeed chrono which hangs off of your barrel fugs up your groups. Never use one during development!

I have a buddy who had a laser beam .223 WSSM. He then wrapped camo tape around the barrel and it turned into a shotgun.


Barrel harmonics happen.... smile


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I hung a 14oz weight off the end of the barrel.... as described above, on a number of guns.... it has never hurt accuracy....

How is that possible?


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Lucky as fug?




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Luckiest guy I know..... you know my girl....

But.... I don't know anybody who shoots a different load suppressed than they do unsuppressed..... do you?

If NOBODY changes loads when they add the can..... and the gun shoots the same.... then it stands to reason that something other than "harmonics" is mostly responsible for the consistency that Audette loads produce...


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No I don't. Suppressors don't seem to affect accuracy like you say, but POI, yes.

I do know that the other examples I gave do.


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[Linked Image]


Harmonics are totally responsible for accurate loads. The entire purpose of the Audette is to isolate the exit time where harmonics are correct for accuracy.

Ever hear of a barrel tuner? What do you think it does? It's nothing more than an weight adjustable for length.


Quote
SUMMARY.... For the reader who doesn't want to wade through all the discussion here is a summary of what a tuner can do to correct for small variations in muzzle velocity from round to round. The Muzzle Projection Curve shows where the muzzle is pointing at a 100 yard target while the rifle is being fired. The most important aspect is the curve is where the muzzle is pointing at the time the bullet exits the muzzle.



Quote
LADDER TEST.... It appears that the "Muzzle Projection Curve" (MPC) plus the Muzzle's Vertical Velocity that is imposed on the bullet at muzzle exit time tends to shed some light on what is going on in the Ladder or "Audette" test. The Ladder Test uses loading to generate a series of loads with increasing velocity shot at the same target to see if some of the rounds print at the same POI even with different velocities. If a convergence is found, then loading in that range of velocity should shoot tight groups even with slight velocity variations. The following calculations were done to find the Point of Impact (POI) at a 100 yard virtual target. In the field, it is typical to shoot the Ladder Test at long range. One thing the 300 yd Ladder Test does it that it amplifies the bullet drop more than where the muzzle is pointing. The muzzle pointing is line-of-sight and therefore linear but the bullet drop during the Time Of Flight (TOF) is not linear with distance. With the calculation it is possible to calculate the POI even if they are close to each other, so 100 yards was used.



Read this entire page and hopefully you'll start to understand....

http://www.varmintal.com/aeste.htm


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Funny how that phenomenon doesn't apply to suppressed rifles.....


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Originally Posted by Dogshooter
Funny how that phenomenon doesn't apply to suppressed rifles.....


I'd say it does, but may not be as noticeable.

Anything suppressed generally has a big heavy barrel. If anything, the weight of the suppressor dampens the barrel harmonics. A friend just put one on an AR chambered in .260. It shot 1 1/4" groups without the suppressor and One-Holes with the suppressor.

Most suppressed barrels are heavy axle rods in the first place.



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A guy named Chris Long came up with something he called Optimum Barrel Time. Seems pretty similar to the Audette theory.

http://the-long-family.com/optimal%20barrel%20time.htm

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There is some 22 benchrest guy who had a theory on tuners for 22's that seemed to work for his guns. Essentially his tuners put a calculated amount of weight out past the muzzle of his guns. He also had some thoughts about barrel harmonics and ringing the barrel that he wrote up in a magazine.

Might be Bill Calfee, but I'm not sure about that.

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Dogshooter, I think you should test your theory by shooting your can on a less than optimum load.

I have a hunch it will be significantly worse.


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Originally Posted by sawbuck
Dogshooter, I think you should test your theory by shooting your can on a less than optimum load.

I have a hunch it will be significantly worse.


Who gives a schitt? A bad load is a bad load..... but you're wrong. Ric sites an example above of a rifle going from 1+ MOA to a one hole gun when the can was added. Also.... I've had several marginal loads that shoot much better through the suppressor. Accuracy has always held or improved...

If the Audette relied solely on harmonics..... then a good load without the can, wouldn't still shoot as well once the can was added..... because the added weight/length necessarily changes the harmonics.

Who changes to a different load once they add the suppressor? NOBODY..... why?


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I'm sure you've heard of the BOSS System. Have you ever tuned a rifle with one?


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I've used a QUE tuner, which works on the same principal as the BOSS. It worked well, making a 1.25" load into a .6" load within about 4 adjustments. Worked as advertised but was VERY loud and I finally got tired of the looks.

John


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Originally Posted by rcamuglia
I'm sure you've heard of the BOSS System. Have you ever tuned a rifle with one?


Yes.... they sucked heavy ass... and the "tuning" was marginal at best.

You ever shot a ladder, picked the best load..... then tried to de-tune the load with the boss? That would be a far more apt experiment here....

Still haven't come up with a good answer for why a suppressor doesn't effect ladder developed loads.... or an example of accuracy getting worse with a can.

There is another explanation other than pure harmonics..... there has to be...


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Actually the BOSS works perfectly and sucks no ass at all.

You can take any factory ammo and make it shoot great by tuning with the BOSS. The ammo can suck complete ass in a bare barrel.

Why can you make it shoot in a rifle with the BOSS? (Barrel tuner)

Because you can change the harmonics of the barrel with minute changes in the position of the weight to suit the ammo.

The reason cans help accuracy and don't change accurate existing loads is because a weight that heavy on a muzzle DAMPENS harmonics even more....like I've already submitted

Have you used a rubber barrel tuning donut like the LimbSaver? They actually work. Why? Because they minutely change the harmonics of a bare barrel.


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All that being said, the only way to make a bare barrel shoot well is to find a load that exits the muzzle at the time when it is consistently pointing at the same place. You find this load by shooting an Audette and noting where consecutive shots have virtually the same POI.

This is called a Harmonic Node

You tailor the ammo to the gun, not the barrel harmonics to a factory load like with a tuner.



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A couple of thoughts-

First, if accuracy dispersion is in both planes, why do we worry about vertical dispersion only and not horizontal dispersion? The reason is that as distance increases, accuracy dispersion becomes a very minor factor with modern, accurate rifles. Gravity and wind are the two major factors that we have to deal with, and wind is so variable that accuracy dispersion becomes immaterial, and is lost in the resolution noise of the wind. Not to mention that after a node is found, minor adjustments can be made to shrink groups and reduce horizontal (and vertical) dispersion. Gravity, however, is consistent, and its effect on projectiles with different muzzle velocities grows disproportionately as distance increases. So we really want to find a way to minimize the POI variation induced by gravity and minor MV differences. To illustrate, if we find a node and work up a load in that node that shoots 0.5 MOA on average, at 1000 yards the mechanical accuracy dispersion of that load is 5.24". So there is a variation of 5.24" of vertical dispersion inherent in the load itself. Now, if we used a 0.625 G1 BC, 3000 fps load with a MV extreme spread of 40 fps, gravity would induce a variation of roughly 11", and that numbers gets bigger the farther out you go. So if we can time the bullets exiting the muzzle so the slower bullets leave when the muzzle is pointing slightly higher, and the faster ones leave when the muzzle is pointed lower, we can largely cancel out that gravity-induced dispersion.

Wind, on the other hand, is unpredictable, variable in speed and direction, and wind drift at 1000 yards dwarfs the 5.24" of mechanical accuracy dispersion. Using our 3000 fps 0.625 BC example, even a 10mph wind can induce 70"+ of deflection.


As to the suppressor accuracy observation, I can think of a couple of reasons to explain increased accuracy when using a suppressor. The first, is that one factor in accuracy is muzzle blast causing bullet upset as the bullet leaves the muzzle. A perfect crown and a well-balanced and stabilized bullet help mitigate the muzzle blast causing instability as it squeezes passed the heel of the bullet. A suppressor reduces this high-pressure force around the bullet as gas escapes, which minimizes bullet upset as it leaves the muzzle. Secondly, it's important to note that finding a node doesn't eliminate vertical dispersion entirely, but it minimizes it within the limits of the "whipping" motion of the barrel. A suppressor does dampen the pressure wave emanating up and down the barrel when ignition occurs. If we have bullets leaving when the muzzle is positioned differently, causing accuracy dispersion, that dispersion is minimized by reducing the positional variation as the pressure wave goes through the barrel. If we magnify the effect of the pressure wave for a minute, imagine that the barrel whips in a figure-8 motion as the pressure wave goes through it back and forth, and that the extreme bottom and extreme top positions differ by 2MOA. That means that in a worst case scenario, if a bullet exited the top of the muzzle's path and another exited at the bottom, the group at 100 yards would be 2". If we hang a weight off the end of the barrel, dampening the harmonic motion so that the positional extremes of the figure-8 only differ by 1MOA, then the group would be reduced to 1".

So, while finding a node and selecting a group based off of a ladder test minimizes the effects of MV variation on a bullet's trajectory at range, reducing the motion itself means inherently smaller groups.

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Excellent points on the accuracy improving virtues of a suppressor.... and I agree, mostly.

But, isn't the point of the ladder to have the bullet exit the bore at a peak or valley in the oscillation pattern?

Dampening affects both amplitude and frequency, creating entirely barrel harmonics.... so hanging the can on, more often than not, would cause the bullet to exit at a new point in the new oscillation pattern. Even though that pattern is now smaller, the odds of the bullet leaving under the identical (ideal) position relative to peak/valley as the pre-can pattern is pretty slim.... thereby negating the advantage of the ladder developed "node in harmonics". Yet somehow, those rounds are not only equally as accurate, but often more accurate.

Furthermore, no one would expect the accuracy of the load to be the same if I said "hey, let me hang this 1lb weight off the end of your barrel while you shoot". But, you're telling me that somehow because it eats up some blast , and slightly "dampens" vibration, the suppressor is exempt from its effect on the oscillation pattern and muzzle position delta that the any other added weight and length create (BOSS, MagnetoSpeed/"tuner", etc.)?


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What makes you think the dampening provided by the suppressor changes the frequency propagated by the ignition and pressure wave initiated at the chamber? The same wave and node pattern should still exist, albeit with a decreased wave amplitude. This theory is borne out by observed results, as you mention.

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Originally Posted by Jordan Smith
What makes you think the dampening provided by the suppressor changes the frequency propagated by the ignition and pressure wave initiated at the chamber? .


Isn't that what dampening is.... decreasing the frequency/amplitude of the vibration?

How is the suppressor's weight different from any other "weight" you could attach to a barrel?


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You fellas should check out this page from Varmint Al's website: [color:#000099]Link to Esten's tuner[/color]

At the top of that page is an animation showing the barrel deformation as the bullet travels down the bore, based on FEA models. The barrel deforms, or bends, but Al states that the oscillations that you dudes are discussing do not occur until AFTER the bullet leaves the muzzle. See quote below, from the link above.

The can/silencer/suppressor acts as a mass damper during the oscillations and changes the deformation of the barrel. If POI is lower with the can/silencer/suppressor, then it makes sense since the muzzle would not project as high.



Quote
CONCLUSION.... Maybe the "consensus" was that a rifle barrel vibrated in one or more of the mode shapes when fired. That was because the mode shapes and frequencies were easy to calculate and they did seem to answer some of the questions. From these FEA dynamic pressure calculations, it appears that the recoil and forced deformations are much more important than the natural vibration modes in determining where a barrel is pointing when the bullet exits the muzzle. Then after the bullet exits the muzzle, the rifle barrel vibrates in its various natural frequencies and mode shapes. Put another way, consider a guitar string being plucked. One pulls the string into a position (forced position) then releases it and the string vibrates at is natural frequency. The recoil and bullet motions "pulls" the rifle barrel to a new shape and once the bullet leaves the barrel, then the barrel vibrates. However, the addition of the scope to the model has shown some small high frequency vibrations superimposed on the forced deformations, both of which, slightly alter where the muzzle points before the bullet exits. For lowering the amplitude of the high frequency vibrations, it appears that even an "out of tune" tuner is better than no tuner at all.

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And for crying out loud, stop using "dampen"! grin

Dampen = moistening

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Damp, damping, damped. Not wetting.

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Also note that Al mentions high frequency vibration in addition to the recoil and forced deformation.

I don't think he states it in that page, but there would be pre-ignition vibration from the firing mechanism, then primer ignition, powder ignition, bullet slamming into barrel, etc. These vibrations would propagate thru the rifle at the speed of sound thru rifle material (steel)... in other words... really fast. But it seems that the recoil and deformations are larger than those smaller vibrations until the bullet leaves the muzzle.

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This might be a fun experiment...

I could record 4 to 6 channels at 131,000 samples per second. That could be one tri-axial accelerometer at the muzzle, a single axis accelerometer at the stock or action, and one microphone at the muzzle for 5 channels. I could also perform an experimental modal to determine the natural frequencies and mode shapes of the barrel.

Processing the data might get interesting though grin

I've heard/read that there is some old high speed video showing what Al describes where the barrel deforms before the bullet exits the muzzle, then oscillates after. I've never seen it, but we could collect data to find out what actually happens.

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Originally Posted by rcamuglia
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Harmonics are totally responsible for accurate loads. The entire purpose of the Audette is to isolate the exit time where harmonics are correct for accuracy.

Ever hear of a barrel tuner? What do you think it does? It's nothing more than an weight adjustable for length.


Quote
SUMMARY.... For the reader who doesn't want to wade through all the discussion here is a summary of what a tuner can do to correct for small variations in muzzle velocity from round to round. The Muzzle Projection Curve shows where the muzzle is pointing at a 100 yard target while the rifle is being fired. The most important aspect is the curve is where the muzzle is pointing at the time the bullet exits the muzzle.



Quote
LADDER TEST.... It appears that the "Muzzle Projection Curve" (MPC) plus the Muzzle's Vertical Velocity that is imposed on the bullet at muzzle exit time tends to shed some light on what is going on in the Ladder or "Audette" test. The Ladder Test uses loading to generate a series of loads with increasing velocity shot at the same target to see if some of the rounds print at the same POI even with different velocities. If a convergence is found, then loading in that range of velocity should shoot tight groups even with slight velocity variations. The following calculations were done to find the Point of Impact (POI) at a 100 yard virtual target. In the field, it is typical to shoot the Ladder Test at long range. One thing the 300 yd Ladder Test does it that it amplifies the bullet drop more than where the muzzle is pointing. The muzzle pointing is line-of-sight and therefore linear but the bullet drop during the Time Of Flight (TOF) is not linear with distance. With the calculation it is possible to calculate the POI even if they are close to each other, so 100 yards was used.



Read this entire page and hopefully you'll start to understand....

http://www.varmintal.com/aeste.htm


Good job 4th

As you can see from the above, I referenced Varmintal's page earlier


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Hey dog,

If barrel harmonics and bullet exit times do not affect load accuracy, please explain what does.

Why does a load at a particular charge and depth one-hole and another, a grain Higher or lower, shoot poorly?


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Originally Posted by rcamuglia
Hey dog,

If barrel harmonics and bullet exit times do not affect load accuracy, please explain what does.

Why does a load at a particular charge and depth one-hole and another, a grain Higher or lower, shoot poorly?


I don't know.... that's what I'm saying.... but again, there's no way that adding a can (or other weight) doesn't change the harmonics. It changes them, period.

So what I want to know is..... if it is purely about harmonics.... how come when you change the harmonics with the can, it never adversely affects accuracy.... even though the harmonics are obviously different?

Is the dampening(?) effect that great?

If so, how come all the bench rest and f-class guys aren't running can's? After all..... it should be far easier to develop loads with those pesky vibrations significantly damped.

I mean, if simply adding a suppressor can remove all the harmonic variables..... then why would you ever develop a load without one?

How come all the rest of the devices designed to damp vibration and modify harmonics, therefore change accuracy, are moveable? Could it be that they realize not every load/barrel needs to be "tuned" the same way?

If I put one of those Limbsaver Tuners on my barrel...... will it possibly make an accurate load shoot worse until I get it in the proper spot where the load jives with the "harmonics"? Why?

If so, why is it that the suppressor somehow works every time to damp vibration, and change the harmonics.... but it is fixed, and never adversely effects accuracy?

Again.... I don't know the answer to your question Ric..... it could be an internal pressure Mecca is achieved, or or the curve is developed at a different rate, or whatever. But the same could be said for changing a primer.... or seating depth, or a lot of powder. I do believe the loads are more stable.... and I believe harmonics is the big piece of the puzzle.....

4th, Jordan..... you're smart dudes, and I appreciate you guys taking the time to reply. Thanks for the grammar lesson Jason.... I tried to take it to heart.



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If your barrel is not properly harmonized, is it still possible to get a "DRT?"



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It is possible to damp the amplitude of a harmonic oscillation without changing its frequency. That was my proposition.

Again, I suspect gas suppression has a large part in achieving accuracy with a can. As you implied, it's an internal pressure thing. If a can reduces the exit pressure of gas around the heel of the bullet from 12k psi to 2k psi, that would contribute less stability disruption to the bullet that running can-less.

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Also,

damp·en
ˈdampən/
verb
1.
make slightly wet.
"the fine rain dampened her face"
synonyms: moisten, damp, wet, dew, water; literarybedew
"the rain dampened her face"
2.
make less strong or intense.
"nothing could dampen her enthusiasm"
synonyms: lessen, decrease, diminish, reduce, moderate, damp, put a damper on, throw cold water on, cool, discourage, disincentivize; More

grin

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Originally Posted by Jordan Smith
It is possible to damp the amplitude of a harmonic oscillation without changing its frequency. That was my proposition.

Again, I suspect gas suppression has a large part in achieving accuracy with a can. As you implied, it's an internal pressure thing. If a can reduces the exit pressure of gas around the heel of the bullet from 12k psi to 2k psi, that would contribute less stability disruption to the bullet that running can-less.


So.... a good ladder load could have less to do with barrel harmonics.... and more to do what happens as the bullet leaves, and immediately after the bullet leaves the bore?

Could there just be a jive between the bore exit pressure, bullet base, and crown shape that has less affect on the bullet than other loads of slightly higher and lower charges?

I wonder what would happen if you took a good ladder developed load, and then changed the crown shape drastically. That would do nothing to the harmonics of the barrel.... but could/would change the accuracy of the load.

If that did happen.... then it would be obvious that Ladder loads have less to do with internal harmonics, than they do with the relationship between pressure, bullet shape, and the crown. Which would also coincide with my theory as to why suppressors nearly always aid in accuracy.... while other "dampners" may not.

Just a thought.....


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You obviously didn't read this:


For lowering the amplitude of the high frequency vibrations, it appears that even an "out of tune" tuner is better than no tuner at all.


Quote
Again.... I don't know the answer to your question Ric..... it could be an internal pressure Mecca is achieved, or or the curve is developed at a different rate, or whatever. But the same could be said for changing a primer.... or seating depth, or a lot of powder.


When you change a primer, depth or power lot, you are changing the pressure.

Changing the pressure changes velocity.

Changing velocity changes exit time of the bullet from the muzzle

The muzzle is moving so changing exit time changes accuracy.

The movement of the barrel is caused by vibrations....Harmonics.



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Dogshooter,

One time I threaded a 10/22 barrel for a couple inches with 9/16X12 threads. Then I threaded a 3/4"X5" bolt to match those threads. Then I cut off the 3/4" threads and parted off a little of what was left to use as a jam nut. The .22 normally fired 1 1/2" groups at 50 yards with five Yellow Jackets. When I first started my test I had no idea how much to turn it to effect a change. After the first group I turned it 1/4 of a turn. The group remained the same size but moved toward 10 o"clock by three inches. So I started moving the barrel weight 1/16 of a turn. Eventually I could always get five Yellow Jackets to make 5/8" groups. The weight moved only about .005" and yet accomplished a lot.


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Originally Posted by Dogshooter
Originally Posted by Jordan Smith
What makes you think the dampening provided by the suppressor changes the frequency propagated by the ignition and pressure wave initiated at the chamber? .


Isn't that what dampening is.... decreasing the frequency/amplitude of the vibration?

How is the suppressor's weight different from any other "weight" you could attach to a barrel?


Maybe a suppressor mostly just dampens the amplitude (strength) of the vibration. This seems to makes sense because the frequency of the vibration should really only change if the barrel material was changed. Then with a can you also get the benefit of the way it handles the pressure wave after the bullet exits the muzzle.
I'm going to have to re-read Rifle Accuracy Facts now. It has a lot of big brain stuff on barrel vibration. Good thread everyone.

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My lightweight Creedmoor is in harmonic tune today.

laugh laugh laugh


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Originally Posted by Jordan Smith
It is possible to damp the amplitude of a harmonic oscillation without changing its frequency. That was my proposition.



Jordan,

I started a new job about 9-months ago that requires me to work on vibration problems. I am by no means an expert but have a very basic understanding of vibrations and mode shapes. Vibration analysis is a very specialized field within mechanical engineering that requires a lot of advanced training/coursework and practical experience... so I am just a hack grin

In our lab, I have done a few "experimental modal tests". We do these tests to understand the natural frequencies and mode shapes of a structure when it gets excited at these frequencies. Remember the Tacoma Narrows bridge!

We basically use a hammer with loadcell in the tip or a shaker to excite a structure. I've only done the hammer test. We suspend the structure with very soft isolators, excite the structure, and collect accelerometer data all over the structure. This data can then be used to create 3D models showing the mode shapes, like the bridge for example.

These different natural frequencies and "modes" are properties of the structure, and it will behave in this way if the frequency is correct for that mode shape. In our tests, the rigid body mode is the lowest frequency where the whole thing moves in space, via the soft isolators. For a rifle barrel, the first vibration mode is generally believed to be a simple bend, with the muzzle projecting up and down... at a certain frequency.

This first mode "shape" is basically the same for most barrels, but the frequency required to create this shape can be changed by altering the stiffness. We can alter the stiffness by chopping the barrel (stiffer) or adding mass at the muzzle (less stiff). Decreasing the stiffness makes the mode frequency lower.

Some BR dudes talk about "slowing" a barrel down. What they are saying is that they want to lower the mode frequencies using the tuners. Their hypothesis is that the bullet exit needs to be during the upswing, and not during the downswing as Varmint Al illustrates at his website.

I'm going out on a limb here, but I think everyone is still thinking about a barrel "whipping" wildly before the bullet exits the muzzle... or "oscillates". Per Varmint Al, this doesn't happen until AFTER the bullet leaves the barrel. The barrel is getting bent (deformed)... as shown in his animations, then the bullet exits.

At Al's site, he listed ~135 Hz as the first mode frequency. This would be 1/135 = 0.007 seconds for one period. But if you assume that the barrel time is 0.001 seconds (also from Al's site), then the bullet exits well before we have one complete vibration period. The bullet exits at 14% of the periodic cycle. This could be during the upswing, but if the natural frequency and excitation creates a higher frequency vibration the barrel could be past the highest muzzle projection and on its way down. Hence, the BR dudes wanting to "slow" the barrel down.

All that to say that I'm not sure that their goal is to reduce the amplitude, as the different modes can be pretty wild looking. Now the actual mode shape and frequency responsible for the muzzle projection, or excitation frequency, is a different story.

Jason

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Originally Posted by Dogshooter

So.... a good ladder load could have less to do with barrel harmonics.... and more to do what happens as the bullet leaves, and immediately after the bullet leaves the bore?

Could there just be a jive between the bore exit pressure, bullet base, and crown shape that has less affect on the bullet than other loads of slightly higher and lower charges?

I wonder what would happen if you took a good ladder developed load, and then changed the crown shape drastically. That would do nothing to the harmonics of the barrel.... but could/would change the accuracy of the load.

If that did happen.... then it would be obvious that Ladder loads have less to do with internal harmonics, than they do with the relationship between pressure, bullet shape, and the crown. Which would also coincide with my theory as to why suppressors nearly always aid in accuracy.... while other "dampners" may not.

Just a thought.....


Dog,

If you search for "traveling wave theory", Chris Long describes what he believes is a pressure ring that runs up and down the barrel. I think he claims that bullet exit while the ring is at the muzzle is bad juju.

I'm not sure anyone has confirmed this or not, but remembered it after reading your post above.

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4th Point, have you read Rifle Accuracy Facts by Vaughn? I don't have the education to understand a lot of what he talks about, but you seem to.

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No, but I'll check it out. Thanks!

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It's probably a good read for someone with an engineering background although dated. I don't have the education to get the most out of it.

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For you guys that shoot ladder tests, do you shoot several ladders and look for a trend? I would think that just shooting it once would introduce a the probability of human error influencing bullet impact points, especially at 600 yards.


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Originally Posted by sambo3006
For you guys that shoot ladder tests, do you shoot several ladders and look for a trend? I would think that just shooting it once would introduce a the probability of human error influencing bullet impact points, especially at 600 yards.


If you can't shoot, you can't shoot.

Factory ammo is perfect for those who fit the bill


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Gee I'm sorry, I thought I asked a legitimate question about the ladder test and repeatibility. Apparently not. Now if you guys will excuse me I'm going to go buy some more factory ammo while rcamuglia walks on water out to his 600 yard target. cool


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Originally Posted by sambo3006
Gee I'm sorry, I thought I asked a legitimate question about the ladder test and repeatibility. Apparently not. Now if you guys will excuse me I'm going to go buy some more factory ammo while rcamuglia walks on water out to his 600 yard target. cool

I know when I saw you here your factory loads were doing a serviceable job for you!!!!!!! laugh

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Yep, that was those factory loaded 7mm STW 168 gr JLKs and that speed goat was only 456 yards. Not even far enough for a decent ladder test!


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Originally Posted by sambo3006
Yep, that was those factory loaded 7mm STW 168 gr JLKs and that speed goat was only 456 yards. Not even far enough for a decent ladder test!
laugh
Probably enuff gun for antelope, I believe..........

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Originally Posted by sambo3006
Now if you guys will excuse me I'm going to go buy some more factory ammo while rcamuglia walks on water out to his 600 yard target. cool


I'm calling BS. Everyone knows you shouldn't shoot across water.



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Originally Posted by sambo3006
Gee I'm sorry, I thought I asked a legitimate question about the ladder test and repeatibility. Apparently not. Now if you guys will excuse me I'm going to go buy some more factory ammo while rcamuglia walks on water out to his 600 yard target. cool


It's a good question but indicates your inexperience with long range shooting. If you can't hold on a 2" dot at 600 with a solid bench rest and squeeze the trigger without moving, then the long range Audette won't work for you. Stick to 100 yard development

I usually drive to the target at 600. Another thing you'll learn with some more experience.

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Originally Posted by Hondo64d
Help me out here. In every description of the various versions of ladder and OCW load development methods I have seen, conventional wisdom says to ignore any horizontal distribution and attribute it to wind. We all know barrels oscillate upon firing but what law of physics makes them only oscillate in the vertical axis? Why don't they oscillate in the horizontal axis too? Or in a combination of vertical and horizontal axis? And, if that is the case, why are we ignoring the horizontal dispersion in ladder and OCW type load development?

Thanks,

John




Now that we have 3 pages of shared knowledge, Lets start again:

If you have a 20 shot ladder at .1 gr one shot steps and you find a 3 shot point (+/- .1) that is very good vertically but not horizontally what are you going to do about it?


...


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That's a good question, but only shows your inexperience with long-range shooting........



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Originally Posted by RaySendero
[quote=Hondo64d]Help me out here. In every description of the various versions of ladder and OCW load development methods I have seen, conventional wisdom says to ignore any horizontal distribution and attribute it to wind. We all know barrels oscillate upon firing but what law of physics makes them only oscillate in the vertical axis? Why don't they oscillate in the horizontal axis too? Or in a combination of vertical and horizontal axis? And, if that is the case, why are we ignoring the horizontal dispersion in ladder and OCW type load development?

Thanks,

John



.1 grain increments are too fine. Generally for .308 size cases .3 grains is good. For magnum cases .5 grains

When you find consecutive shots that have nearly the same POI, you then shoot those individual loads to test. Pick the best and make seating depth adjustments if needed

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This was an entire 560 yard Audette. The impacts were all so close together that I didn't bother to mark them. I chose the highest velocity load under pressure

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Chosen from an Audette


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6.5 Creedmoor/139 Scenar/H-4350

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600 yard group with chosen load


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Originally Posted by rcamuglia
Originally Posted by sambo3006
For you guys that shoot ladder tests, do you shoot several ladders and look for a trend? I would think that just shooting it once would introduce a the probability of human error influencing bullet impact points, especially at 600 yards.


If you can't shoot, you can't shoot.

Factory ammo is perfect for those who fit the bill


My question still stands. I doubt very many of us can be supremely confident that there is absolutely no movement of the rifle during barrel dwell time of the bullet.

I have no doubt that I have far less experience than you at long range shooting but I do have access to a 600 yard range and have flung a fair amount of bullets out at the 4, 5 and 600 yard targets from both the bench and prone with bipod with some pretty accurate rigs. I've done a fair amount of load development with chronograph and shooting for groups at those ranges, just haven't done a ladder test yet, hence the question.

Not trying to start a pissing contest here but I think your response to my original post was not productive in the least and came off as arrogant and rude. I'll not post any further on this threat except for questions related to ladder tests in an effort to get it back on topic.


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Sorry you felt that was as that was not my intention. I was simply answering your question.

The point is that if your shooting skills are at a level where you can't be consistent enough to not affect the test, it doesn't matter what range you try to develop a load. Piss poor shooting fundamentals will affect results and a guy might as well shoot factory ammo.



Originally Posted by Bristoe
The people wringing their hands over Trump's rhetoric don't know what time it is in America.
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Originally Posted by sambo3006
Originally Posted by rcamuglia
Originally Posted by sambo3006
For you guys that shoot ladder tests, do you shoot several ladders and look for a trend? I would think that just shooting it once would introduce a the probability of human error influencing bullet impact points, especially at 600 yards.


If you can't shoot, you can't shoot.

Factory ammo is perfect for those who fit the bill


My question still stands. I doubt very many of us can be supremely confident that there is absolutely no movement of the rifle during barrel dwell time of the bullet.

I have no doubt that I have far less experience than you at long range shooting but I do have access to a 600 yard range and have flung a fair amount of bullets out at the 4, 5 and 600 yard targets from both the bench and prone with bipod with some pretty accurate rigs. I've done a fair amount of load development with chronographI'll not post any further on this threat except for questions related to ladder tests in an effort to get it back on topic.



You're threatening to piss in a contest with me?

LOL


Originally Posted by Bristoe
The people wringing their hands over Trump's rhetoric don't know what time it is in America.
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Fair enough. No sore mangina on my part. Although I do think I can take you in a pissing contest. I can dot the eye of a cheerio with a first round hit all the way across the room from the toilet. I developed that load with a ladder test but my wife got mad at me for not cleaning off the impacts of the hotter loaded rounds from the lid. grin


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Been "checking the harmonics" eh?

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Originally Posted by sambo3006
Fair enough. No sore mangina on my part. Although I do think I can take you in a pissing contest. I can dot the eye of a cheerio with a first round hit all the way across the room from the toilet. I developed that load with a ladder test but my wife got mad at me for not cleaning off the impacts of the hotter loaded rounds from the lid. grin


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Originally Posted by Bristoe
The people wringing their hands over Trump's rhetoric don't know what time it is in America.
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Originally Posted by smokepole
That's a good question, but only shows your inexperience with long-range shooting........



LOL - I maybe inexperienced

BUT - You are too ignorant to answer a simple question!

Last edited by RaySendero; 02/09/16.

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Ray, you're killing me, it was a joke, man!!!



A wise man is frequently humbled.

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Everyone's feelers get hurt around here.

Lighten up!


Originally Posted by Bristoe
The people wringing their hands over Trump's rhetoric don't know what time it is in America.
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Harden up chopper Reid, Google it!!



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LOL!






Originally Posted by Bristoe
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Originally Posted by smokepole
Ray, you're killing me, it was a joke, man!!!



Whatever, joke, playing - Your post screw-up my whole points on topic.

The OP asked about ignoring the horizontal.

Just think about this in reverse: If you WERE to find a good (small) vertical response point shooting a ladder, you wouldn't ignore the vertical because of a bad horizontal ?!

No - You should further test that point shooting some groups. The ladder IS NOT the end of your testing, its the starting point!


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Ray, I understand the question. My answer is, there's more than one way to skin a cat. Or find an accurate load. Or use the results of a ladder test.

Personally, I've tried them. Now I just find a load that shoots good at 100 and then stretch it out and see if it holds up at long range. Works for me.

I guess that just shows my inexperience with long range shooting too, but that's a burden I'll have to bear.



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Originally Posted by smokepole
Ray, I understand the question. My answer is, there's more than one way to skin a cat. Or find an accurate load. Or use the results of a ladder test.

Personally, I've tried them. Now I just find a load that shoots good at 100 and then stretch it out and see if it holds up at long range. Works for me.

I guess that just shows my inexperience with long range shooting too, but that's a burden I'll have to bear.




Smoke,

Actually my preferred method is also to work-up loads at 100 yds and then stretch it out to longer range groups, too. Because most of my hunting is within 200 yds. I've only used the type of ladder described for 2 rifles that did double duty as LR hunting and targets where I had expectation/possibility of 300 to 600 yds shots. Thus since I had already done some load work-up I could use smaller 0.1 grain steps and 20 shots would cover 2 full grain load spread. If you have a dedicated LR rifle and haven't tried it out - Just do it. 20 shots at 300 yds in an afternoon range session will be fun.



OK back to topic - My second point I was going to make:

We have some great info and theories in these 3 pages. But it should always come down to shooting the groups at the range yardages you expect to use'em.




Ray
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