What is a "Node"?

[Bart B.]

Have no interest in how it vibrates. All this physics is not going to change where my bullet goes one bit.

You're both OK and right with your thoughts.

Some folks have an interest in knowing why their bullets go where they are fired. A few come up with ways to compensate for some variables so bullets land closer together on target. Best example I can think of is tuning weights on barrels' muzzle end. Very popular these days in benchrest and rimfire match rifles. There are many who think they're an emotional crutch and do nothing because the barrel is motionless until after the bullet is gone.

 

[Richard Coody]

You're both OK and right with your thoughts.

Some folks have an interest in knowing why their bullets go where they are fired. A few come up with ways to compensate for some variables so bullets land closer together on target. Best example I can think of is tuning weights on barrels' muzzle end. Very popular these days in benchrest and rimfire match rifles. There are many who think they're an emotional crutch and do nothing because the barrel is motionless until after the bullet is gone.

Oh yeah

Tuners are great. They work very well but show me the.computer program that tells me where to set it for my rifle, load, bullet and shooting style. It is still trial and error

Like caffe said. Stop the muzzle.

 

[JRS]

You're both OK and right with your thoughts.

Some folks have an interest in knowing why their bullets go where they are fired. A few come up with ways to compensate for some variables so bullets land closer together on target. Best example I can think of is tuning weights on barrels' muzzle end. Very popular these days in benchrest and rimfire match rifles. There are many who think they're an emotional crutch and do nothing because the barrel is motionless until after the bullet is gone.

As the bullet is forced into the lands of the barrel, the bullet obtains forward momentum and rotational speed. Interaction of the bullet within the barrel acts as excitation force and the barrel vibrates.

 

[Richard Coody]

As the bullet is forced into the lands of the barrel, the bullet obtains forward momentum and rotational speed. Interaction of the bullet within the barrel acts as excitation force and the barrel vibrates.

Yep

Makes you sound very smart. Now how does all that information help you hit your target

 

[JRS]

Yep

Makes you sound very smart. Now how does all that information help you hit your target

The reply was for Bart B.

Hitting the target is your responsibility.

 

[savagedasher]

Oh yeah

Tuners are great. They work very well but show me the.computer program that tells me where to set it for my rifle, load, bullet and shooting style. It is still trial and error

Like caffe said. Stop the muzzle.

I think it doesn't stop the the muzzle
But increase the dwell time in the movement
That is why you a tune with a tunner you will find both above and below the point of aim Tune
With a barrel timed up or down seems to be easier to tune .
I never have found the tuneing a load then installing tunner is the way to go .
Larry

 

[Bart B.]

Regarding that "node" at the top and bottom of the muzzle axis whip cycle, and Bill Calfee's oft time claims to tune barrels so they are "stopped" at the peak, here's one barrel maker's take on it:

The influential American rimfire gunsmith Bill Calfee, in an article written for Precision Shooting Magazine ("I'm Feeling Those Good Vibrations AGAIN!" Vol. 52, No. 11, March 2005) presented a rather novel view on how barrels vibrate, and also expressed his belief that for best accuracy, barrels should be tuned so that the muzzle is "stopped" and there is no change in muzzle angle, or position, as the bullet is launched. It should be noted that Calfee's theories have absolutely no basis in fact and are mathematically untenable. But that does not stop it being the most quoted work in the popular press on barrel vibrations and the tuning of barrels.

Bullets leave at different velocities at that point because the pressure curves pushing them are not consistent in shape. Not much compensation for muzzle velocity spread with the barrel stopped compared to the compensation that can be had on the muzzle axis upswing. Barrel stopped for less than a microsecond, before then the muzzle angle is increasing, afterwords it's decreasing.

 

[Bart B.]

As the bullet is forced into the lands of the barrel, the bullet obtains forward momentum and rotational speed. Interaction of the bullet within the barrel acts as excitation force and the barrel vibrates.

That adds to where the barrel starts vibrating, in my way of thinking this out. There's enough shock to make scope reticles wiggle when dry firing and the striker stops against its shoulder in the bolt. 9 fps speed and 2 to 3 ounces of pin (striker?) weight converts to foot-pounds of energy.

I think the barrel starts to vibrate when the case slams into its headspace stop from the force of the firing pin striking the primer. That often sets shoulders back a thousandth or more, so the energy transferred to the barrel has to be expended someplace. That's when the barrel starts wiggling.

 

[Richard Coody]

Watch this. Could you possibly define that in a mathematical equation?

Watch the 50 BMG

https://www.google.com/search?clien...bih=388#scso=uid_WWe5xQAJ20UKg8qMkgUS3Q_1:744

 

[Bart B.]

Mr. Mallock did that a century ago as detailed in the following link:

https://archive.org/details/philtrans05900167

Download the .pdf file, open it, then learn what I did years ago.

Here's an example of the math:



You can buy computer software (Finite Element Analysis) that does that today that uses the complete rifle data converted into cubic millimeter parts then computes their interaction from external forces. Costs a couple thousand dollars for good ones but worth the expense for all the fourth order equations used to calculate the physics involved. Varmint Al's website has examples of some results that cost nothing to study.

Meanwhile, trial and error methods to pick a load that puts all bullets atop each other on target is the best compromise. You just have to shoot enough bullets per test to be statistically significant and meaningful representing where all shots will go.

 

[Richard Coody]

Mr. Mallock did that a century ago as detailed in the following link:

https://archive.org/details/philtrans05900167

Download the .pdf file, open it, then learn what I did years ago.

Here's an example of the math:

View attachment 1015231

You can buy computer software (Finite Element Analysis) that does that today that uses the complete rifle data converted into cubic millimeter parts then computes their interaction from external forces. Costs a couple thousand dollars for good ones but worth the expense for all the fourth order equations used to calculate the physics involved. Varmint Al's website has examples of some results that cost nothing to study.

Meanwhile, trial and error methods to pick a load that puts all bullets atop each other on target is the best compromise. You just have to shoot enough bullets per test to be statistically significant and meaningful representing where all shots will go.

I am quite familiar with finite element analysis. I certainly wouldn't want to be the one to try to input the parameter for all the variables in this problem

Did Mallock just use an X and Y axis. That is what it looks like to me. Gets a little more complicated when you throw in the Z.

 

[Bart B.]

How much does a .003" diameter difference across a 28" AMU taper (1.200" to .900" 30 caliber (.0736 square inch bore area) barrel change its resonant frequency?

From 50.53 Hz to 50.62 Hz. Insignificant for a barrel .003" bigger in diameter and 5/8ths ounce heavier.

 

[dcali]

A node is just shorthand jargon for a good load. Far too many shooters see pictures of barrel vibration "modes" which are harmonic in nature and assume that is what the barrel is actually doing when fired. It is not. This confusion is what leads people to seek out "nodes". Rather than fight the common nomenclature in a righteous fight for truth, it's easier just to accept it.

 

[dcali]

Also, that "stop the muzzle" stuff is 100% Grade A BS. It rivals flat earth theory in its wrongness.

 

[Richard Coody]

Also, that "stop the muzzle" stuff is 100% Grade A BS. It rivals flat earth theory in its wrongness.

Well

Caffe might have the scientific jargon a little confused but he sure can make a .22 rimfire shoot.

Think of the forces going on in that barrel in that barrel in the miliseconds after firing. The force of the initial ignition. Torsion from the bullet engaging the rifling. Elongation from the same thing. And all these forces traveling down the barrel like a wave. But there are several waves. Some traveling faster than others.

Think of the barrel as a cantilevered beam.

 

[dcali]

I'm sure his rifles shoot well. But his explanation is so far off that it really can't be refuted other than to say "that's totally wrong".

 

[nmkid]

I stayed at a Holiday Inn Express and I still don't get it!!

 

[dmoran]

 

[JLT]

Watch this. Could you possibly define that in a mathematical equation?

Watch the 50 BMG

https://www.google.com/search?clien...bih=388#scso=uid_WWe5xQAJ20UKg8qMkgUS3Q_1:744

Yep.

 

[Richard Coody]

I'm sure his rifles shoot well. But his explanation is so far off that it really can't be refuted other than to say "that's totally wrong".

I got his name wrong. It is Bill Calfee. Sort of an opinionated figure that causes lots of controversy. But you sure can't discount his accomplishments.

You should read some of his stuff.