Home Forums Hunting & Shooting Long Range Hunting Why do we ignore the horizontal?

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...

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.

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.

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.

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.)?

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.

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?

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.

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

Dampen = moistening



Damp, damping, damped. Not wetting.

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.

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

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.

Good job 4th

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

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.

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

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.

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

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.....

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.




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.



Learn it, know it, live it Grasshopper...

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.