Im way green on this issue but some elements I could see being a major factor are;

-bbl length

-bbl twist rate

-bullet (the greatest variation??)

-velocity

-powder

-bbl quality

-other load specifics (ie;brass, primer, etc.)

The reason Im asking this is that Im wondering if these things are broken down if perhaps then some common ground could be found, if not for harmonics in general than perhaps within some of its elements.

Your thoughts?

WoW... This idea of eliminating harmonics is way beyond the scope reality. So many factors are involved that cannot attributed. I will have to say that regardless of what conponents you use, your rifle will always want to "vibrate". That is... regardless of what conponent you change it will only be changing vibration perameters. Its unknown even whats good or bad or efficatious in this field. If you want pass/damp'n certian freq... look at the bedding.
just some thoughts
smallfry

I suppose I deserved that.

Look at it this way smallfry, If given the exact same bbl, exact same load, and exact same everything will two bbls vibrate in a "similar" fashion? Surley they will moreso than two completly oppisites. Not trying to eliminate anything here, just trying to get closer to understanding.

There is some thought to the similar vibratons. That is why the BOSS systems on Browings come with a starting guide where to set the BOSS for a certain caliber and bullet weight. With handloading we get in even more variables, bullet weight and shape, powder charges and burn rates, etc.

Hcliff

(damn hair trigger!)

[ 11-29-2002, 21:08: Message edited by: Wstrnhuntr ]

I know I'm getting long in the tooth, but I think some if not most of this "Harmonics" is BS. Carrots are good for you eyes, but eat a truck load of them and go to your eye doctor and ask him if your sight has improved. I think this Boss stuff is marketing, however I do like the name they gave it, " The Boss", kind of makes you feel important. I'm not saying there would never be a use for these things (my guns don't need them), but you have to ask yourself why do their guns need them. I have not seen one yet at the range that will out shoot my guns and I'm really not to proud of mine. There are other less complicated and understandable things Browning could to do to make their guns more accurate. This sounds like something the Kingfish is trying to sell Andy.

Peapicker

If MY understanding is correct, bbl harmonics, really cannot be eliminated. The general thought seems to be to make them consistent. The basic idea being that the bullet leaves the bbl at the same point/moment during the harmonic vibration. I have a rifle that as you increase the powder charge and subsequent velocity, for SOME of the increase the point of impact actually lowers, with little or no change to point of impact left or right. This is due to the bullet leaving the muzzel during a different point in the bbl vibration, but the bullet reaction to increases in powder charge was not as expected, harmonics were consistent in the left/right plane but changed in the vertical. I have another rifle that will change point of impact right several inches with a change in powder charge, a different set of harmonics at play here. So much is/can be at play here. There are, as you question, certainly some that have a greater effect than others, bullet style and weight, powder charge, neck tension, and generally anything that effects chamber pressures, seems to have the greater influence. Handloading doesn't so much eliminate the varibles as it does 'corrals' them.

Hope this helps, Muffin.

Think about a barrel as a giant tuning fork, or even an anvil. When you strike either with a hammer it yields a tone from the vibrations, regardless of how minute those vibrations may be. It's those vibrations that produce the tone ergo the harmonics. In a rifle barrel all those factors mentioned earlier minutely affect those vibrations. The bullet exiting the vibrating barrel will be affected in some way by those harmonics.

I have a Savage 110 30-06 that I recently tried some Speer 200 grn spitzers in. They consistently shot way low and to the right, about 6 inches so. I cant help but think that another gun of the same design might produce similar results but that perhaps one of different manufacture would not.

Like I said... there are so many things related to this subject that are undeterminable a guy would be just chasing the smoke trail he is blowing out of his ass. Rifles today if made well can yield accuracy far beyong anything I could prove in the field.
just some thoughts
take care
smallfry

Here are some other thoughts... These Freq waves travel very fast in steel, every aspect of fireing a gun will cause vibration and cause vibration change, springs, primer ignition, screws, any metal appendages, contact of metal/plastic/wood, anything you can think of. Bullets traveling down the barrel dont pattern one wave but tens of thousands. When you throw a large stone into a pool of water the waves reflect off the shore and hit other outward moving waves, causing disruption and change of Freq. Now imagine taking that pool of water and making hundreds of small undefinable shaped islands in the pool, then throwing thousands of stones in the pool... Chaos.
I imagine it would be easier to build something that would pass/not pass certian freq. then trying to understand what exactly is going on. One playful idea is when you take a strong magnetic weight and slide it up and down the barrel of your 22 to find the "sweet spot". The magnitism has nothing to do with this action other then to hold the weight to the brl. The weight passes certain freq. I have tried this with mixed results.
For the most part I just try to practice in the field or random ranges positions, most of my guns can out shoot me anyways.
Take care
smallfry

WesternHunter,

The greatest variable with regard to where the bullet prints on paper is the recoil arc, rather than the barrel's harmonic whip.

As the rifle recoils upward, the bullet is moving down the barrel toward the muzzle. The longer the barrel time, the higher the muzzle will be in the air when the bullet exits. Of course longer barrel time also entails a slower bullet in the first place, so it drops faster.

Every barrel is going to be different, even if they are from the same model rifle. Would another Savage 110 in 30-06 print that same load to about the same POI? Probably close, but not exactly. This assumes that both were zeroed with another identical load first, and that bedding, action screw torque, etc., were the same also.

The muzzle vibrates in an oblong "figure 8" in most cases. Sporter barrels have larger harmonic whip ranges than heavy barrels. The idea is to get the bullet to exit when the muzzle is at a stable portion of this figure "8". This would be at one end or the other. Bullets which exit the muzzle in the "straightaway" portion of the figure 8 will often print in a straight line on the target. When you see a straight line, you normally can tighten the group with a little more or a little less powder, which brings the bullet's exit point to a stable portion (the end) of the figure 8.

As some of you know, my load development method ignores the barrel harmonic's effect on POI in the initial stages. I do not (as Creighton Audette did) advocate changing an ideal powder charge (optimal charge weight, or OCW as I refer to it) in order to get onto a barrel's harmonic node.

My load development process is described elsewhere here and in other locations on the internet, so I won't go into that in this thread. Suffice it to say that my method of getting an already good load onto the barrel's harmonic "node" is through seating depth variations.

Dan Newberry
green 788

Dan, could you post a link to your method?

I have always, for a while now anyway, loaded one cartridge at every .2gr to .5gr increments in a velocity range I want to be in, then noting the impact for each charge weight to see where they group together over a grain or two spread for a stabile load. One would assume the bullets exit is on the node if a range of loads all group together, and the load in the middle would be the most stable and tolerant of changes.

Thanks, Russ. I had forgotten about that thread...

As mentioned there, Creighton Audette fired his test at 300 yards, and he shot consecutive increased charges at the target and watched for a "cluster" among the vertical string.

In my opinion, 300 yards is too far to conduct the initial test, and one variation of each charge isn't enough to be conclusive. Further, during an extended string of shots, many rifles will build up fouling too quickly to yield good results with charges fired later in the string.

What I did was basically examine what Audette was trying to do (and his "ladder" method did often work) and engineered some changes which made the test easier to perform, and more conclusive.

Audette also began with, and stayed with, one cartridge OAL (seating depth). In my opinion, the seating depth should be determined in the final "fine tuning" stages of development.

Loads developed in the manner I describe in the link that Russ posted above generally shoot well in the majority of rifles chambered for the cartridge in question. Seating depth tests are normally all that need to be done to fine tune such a load to an individual rifle's barrel harmonics.

Current loads developed in this manner, which have proven excellent performers in several rifles are:

.223 Remington 55 grain bullet, 26.6 grains W748

.308 win 175 grain Sierra Matchking, 45.0 grains
of Varget, with CCI BR primer for your
best results.

.243 win 60 grain Sierra HP, 39.8 grains IMR
3031

30-06 165 grain bullet, 57.5 grains of IMR
or H4350 (either works well)

Thanks for the interest,

Dan Newberry
green 788

Thanks guys, interesting variation Dan.

One thing I like to do differently maybe is check a broader charge range. Yours seemed a little narrow, at least with that test anyway.

The last test I did was with my 300 Ultra and RL25 with 180 Sciroccos and 168XLC's.

The load range with the 180 was a bit large but was 85.0 - 97.0gr in 1/2gr steps. 25 rds if I remember.

The load range with the 168 was 94.5 - 99.0gr in 1/2gr steps. 10 rds were fired.

I started about 1-1.5gr lower with each than I really wanted to test, they were basically fouling shots to get settled in, but pressure, velocity and target coordinants were still noted by the Oehler 43 as well.

To make a long story short, I found a sweet spot with each bullet at the upper 60-65k psi level and have verified them both since. They were initally shot then verified at 300 yards.

With both loads, bullets were all over, a little more than normal, no vertical pattern, just all over about 5-7 inches. The 180 put 91.0 - 93.5gr in a group under an inch, 6 rds.

97.0 - 99.0gr, 5 rds, with the 168 went under an inch as well, but under that, they were left, right, up and down, about a 7" spread too.

I settled on a 92.5 and 98gr load respectivly.

Harmonics were definately very sporatic on the edges with this rifle, maybe because the factory contour is so thin and it is a 26" tube and a bit more recoil than the 308 and 300wm.

I've never really just seen just vertical stringing alone with this method as one might think, but more of a loosness as it comes up somewhat overall at places. No doubt the 100 yard zero is changing too, (while shooting at 300) so it really doesn't mean anything during the test if the lower velocity load is shooting flatter at 300 even if it is hitting higher than the faster load. Another thing associated with barrel time and harmonics I assume.

I know I might be missing a load in a tighter range by not shooting groups on the way up, but if I get 3-5 rounds together I usually have a stable load right in the middle, especially if the velocity stabilizes in the same range with it.

[ 11-30-2002, 09:55: Message edited by: Brent Moffitt ]

Brent, Thanks for sharing your perspective.

My own way of looking at the lower charges is that load density normally helps consistency of ignition, and usually makes for a better overall load. That is my own reason for beginning with a charge that is "safely close" to the max.

Also, if I must back too far away from the maximum potential of the load to find a consistent recipe, I might be making a .223 out of a 220 Swift, so to speak.

So if I find that the OCW test does not deliver at the upper range with a particular powder and bullet, I move to another powder. Normally, the slowest powder that will get the job done is best, though some cartridges do very well with the lower densities of the faster powders (IMR 4895 in the 6.5 x 55 Swede comes to mind).

I have found that by careful powder selection for the bullet being used, the OCW load development method will get you a good recipe with only 15 to 18 shots fired in the initial test phase, and perhaps another dozen or so shots with the OAL fine tuning. This spends a minimal amount of components, and uses the minimal amount of bore life.

Take care, and thanks for your words,

Dan Newberry
green 788

Oh, and by the way...

It sounds like you have some really good loads worked up for that 300 RUM. That's a deep accuracy groove you've identified there, and those loads should serve you well in a variety of temperatures and conditions. Good work, for sure...

Dan

"Accuracy Facts" 1998 by Harold R. Vaughn has chapter 4 on "Barrel Vibration".
He show some initial excitation of the barrel having some different modes, but when the bullet exits, it is best just modeled as a 6k~9k Hz sine wave of position of impact corrected for velocity.

That suggests to me that the harmonics are not important like the fundamental.

[ 11-30-2002, 22:48: Message edited by: Clark ]

Westrnhuntr;
If I haven't completely missed the topic, I'am in agreement with most here. This is my understanding of barrel harmonics and their effect on accuracy.
You cannot remove barrel harmonics, only adapt to them. It's my understanding that from a pure accuracy standpoint the lower your shot to shot velocity deviation the tighter your groups should be. The reasoning behind this being; the bullets should exit the barrel at the same point in the vibration cycle. This is the theory behind the BOSS system. -memtb

Harmonics refers to a rifle barrels vibration pattern when the bullet is passing down the bore, nothing more, nothing less. Pretty hard to disect such a simple factor in any rifle barrels reaction to a bullet passing through it's bore. Reloading allows the shooter to tune his load to that particular rifle barrels harmonic pattern for best accuracy. No rocket science needed in the answer to this question. The more you cloud the water the less you see lurking there. the more you digress about that suject the more cloudy the water becomes. just as I am doing with this answer to your question.

Well said Rldr66 and thanks to all who contributed. I now have a better understanding.

The barrel movment is the fundamental frequency PLUS the harmonics [if there are any harmonics].

A pure sine wave has no harmonics.

Example:
A barrel vibrates with the following freqencies:
The fundamental frequency of 8, 000 Hz [cycles per second] has an amplitude of .01"
The second harmonic of freqency 16,000 Hz has an ampltude of .005" with a node in the middle of the barrel
The third harmonic has a frequency of 24,000 Hz and has an amplitude of .002
The fourth harmonic has a frequency of 32,000 Hz and has an amplitude of .001"