Node !!

[K22]

Great statements,

I have mentored more than one shooter who now beats me in matches on a regular basis, using the exact same things I use.

They are simply better shooters.

No truer statement even uttered.

Had the same experience in the late eighties. Mentored a new shooter in precision pistol using the Army Marksmanship Pistol Guide, the best publication ever written in my opinion on the essentials of precision pistol marksmanship.

I was a fairly accomplished precision pistol competitor with an NRA Distinguished Expert Rating. Within 2 years Brian drew even with me then surpassed me. By the mid 90's, arthritis had claimed my shooting arm elbow, and I was out of the sport, but Brian continues to excel to this day.

I never encounter a competitive pistol shooter that could handle match pressure like him, ice in the veins. Among other marksmanship skills, I believe this was one of the essentials for his rise to the top on our team.

 

[Bottom Fodder]

I wish I had “node” about the node 30 years ago then I could have used that to cover for my bad shooting

 

[grovey]

My question is... Guys talk about shooting the low node or shooting the high node. Are all accuracy nodes in a given barrel capable of shooting as tight as each other?

 

[CA_Shooter]

You've almost got it. Part of it at least. Barrels (like any object) have multiple resonant frequencies. how they vibrate depends on the frequency (frequencies, really) of the driving force. In very simple systems it's possible to excite only one "mode" or resonant frequency. In real world systems, many get excited at the same time. So you wind up with a complex dynamic motion of the muzzle. It's moving and deforming in 6 degrees of freedom - sideways, back to front, up and down, plus the three axes of rotation (roll, pitch, yaw). The precise orientation and motion of the muzzle as the bullet leaves determines the initial conditions for the bullets path.

Different charges will produce different velocities and drive the barrel vibration slightly differently (because it changes the driving force). When put all together, you can have the vibration cancel out the velocity variation. One of the predominant driving forces in a rifle is the imbalance in support and mass distribution in the vertical plane. Because of that, you get a large up/down component to the muzzle motion. That's why positive compensation is so easy to see relative to other barrel motion effects. It's not possible to calculate this motion precisely enough to be useful. Measuring it is extremely difficult and impractical. But we can see the effects on the target.

It's important to note that this is not all there is to what makes a load good. It's my belief/opinion that there is simply a great deal we do not understand. Some things we do, but we probably don't know more than we do. Some things we kind of understand but not well enough to be truly useful.

At the end of the day, we're rapidly approaching academics at this point. That's fine and I personally enjoy it for its own sake, but you don't need to understand how something works if you just want to print small groups. Knowing that it works is enough.

One thing that is difficult for me to understand, theoretically, is that for Positive Compensation to be real and consistent - then the barrel at a given charge weight, ambient temperature, and seating depth, THEN the barrel would need to vibrate at the same speed and exact directions over and over again.

 

[CharlieNC]

One thing that is difficult for me to understand, theoretically, is that for Positive Compensation to be real and consistent - then the barrel at a given charge weight, ambient temperature, and seating depth, THEN the barrel would need to vibrate at the same speed and exact directions over and over again.

True. It is unlikely that the offset via PC is ever perfect, as evidenced by the node not being perfectly flat but rather just less sensitive. And the velocity, and consequently barrel time, vary with ambient conditions. From my work I surmise the pertinent vibration, ie the longitudinal speed of sound, varies less.

 

[seymour fish]

Positive compensation is real, and provides for a flat point of impact vs charge weight response. The associated barrel vibration occurs at the speed of sound along the length of the barrel, not traditional transverse barrel vibration view. I presented a lengthy review about this last year with an absence of much discussion, which I had hoped would generate more opinions and insights. Seems it's a topic where speculation is more interesting than the grunt work of analysis.

Real, and the system can be designed to produce it. If desired.

 

[Straightshooter1]

You've almost got it. Part of it at least. Barrels (like any object) have multiple resonant frequencies. how they vibrate depends on the frequency (frequencies, really) of the driving force. In very simple systems it's possible to excite only one "mode" or resonant frequency. In real world systems, many get excited at the same time. So you wind up with a complex dynamic motion of the muzzle. It's moving and deforming in 6 degrees of freedom - sideways, back to front, up and down, plus the three axes of rotation (roll, pitch, yaw). The precise orientation and motion of the muzzle as the bullet leaves determines the initial conditions for the bullets path.

Different charges will produce different velocities and drive the barrel vibration slightly differently (because it changes the driving force). When put all together, you can have the vibration cancel out the velocity variation. One of the predominant driving forces in a rifle is the imbalance in support and mass distribution in the vertical plane. Because of that, you get a large up/down component to the muzzle motion. That's why positive compensation is so easy to see relative to other barrel motion effects. It's not possible to calculate this motion precisely enough to be useful. Measuring it is extremely difficult and impractical. But we can see the effects on the target.

It's important to note that this is not all there is to what makes a load good. It's my belief/opinion that there is simply a great deal we do not understand. Some things we do, but we probably don't know more than we do. Some things we kind of understand but not well enough to be truly useful.

At the end of the day, we're rapidly approaching academics at this point. That's fine and I personally enjoy it for its own sake, but you don't need to understand how something works if you just want to print small groups. Knowing that it works is enough.

Totally agree that one doesn't need to understand how something works, just that it does by what we see on our targets.

I liken it to driving a car, in that one can operate a car just fine knowing little to nothing about how it all works. But if you're driving a dragster to compete, you'd better have someone working on your vehicle that has really good knowledge of how it all works.

 

[Straightshooter1]

My question is... Guys talk about shooting the low node or shooting the high node. Are all accuracy nodes in a given barrel capable of shooting as tight as each other?

From what I've observed in my limited experience . . . yes, they're just as capable, except various velocities are effected differently by external ballistics (e.g. wind).

 

[dcali]

One thing that is difficult for me to understand, theoretically, is that for Positive Compensation to be real and consistent - then the barrel at a given charge weight, ambient temperature, and seating depth, THEN the barrel would need to vibrate at the same speed and exact directions over and over again.

The trick with this stuff is not so much the concepts, but quantifying their effects. The frequencies of vibration are very consistent. Unless you hold the rifle a little differently, or the temperature changes, etc... The pressure curve of the powder will change a little too. When that happens, the frequency content of the driving force changes a little, as well as the amplitude. So yeah, none of it is going to be exacly the same from shot to shot. The question is "what dominates?" is the velocity variation so high that it doesn't matter much what the rifle does? Or the other way around? I think from experience, we can comfortably say that the variable vibration is small enough for the whole PC to work reasonably well. Could I predict that ahead of time? Hell no. There's just too much going on. You have to test it and see. Honestly, the fact that PC works is amazing to me.

Side note: vibrations is a somewhat misleading term. We're not talking about a tuning fork. The physics are the same but what we're really getting after is the *transient* dynamic movement of the muzzle under recoil. By the time a steady state tuning fork vibration has set up, the bullet is long gone. It's not a simple motion.

 

[praveen]

Thank you guys. I’ve some more information on my hands. That doesn’t mean all my queries are solved but its a good start.
I believe there were some others who may have had similar doubts. I’m glad a lot of useful information was shared, not just for me, but for everyone who ends up reading this thread.

 

[ronsatspokane]

Thank you guys. I’ve some more information on my hands. That doesn’t mean all my queries are solved but its a good start.
I believe there were some others who may have had similar doubts. I’m glad a lot of useful information was shared, not just for me, but for everyone who ends up reading this thread.

Anytime man. I'll give you another lesson on noodling your shots into the X ring next Sunday.

 

[Benchrest Braxton]

I don’t have anything to say on nodes, but….

I think there is alot more going on (or less) than what we realize that makes up a guns final precision.

I have had a few factory guns with absolutely terrible looking barrels that was shooting ammo with terrible brass, 100 fps ES, not fireformed, shoot 1/4-1/2 moa ALL DAY at 100 yards.

Normally, a bad looking barrel (pitting, severely fouled) and terrible brass (3+ thou of neck thickness difference side to side) would be used as a source of lack of precision, but that wasn’t an issue at all in my case.

Now why would that be? I think alot of the things that we do don’t make a damned difference besides make us feel better.

Like cortina says, I have 10 steps my reloading process, but only need 5, the problem is i’m not sure which 5.

 

[wildcat3d]

Let the show begin!

I'll join you if I may.

 

[K Hope]

You've almost got it. Part of it at least. Barrels (like any object) have multiple resonant frequencies. how they vibrate depends on the frequency (frequencies, really) of the driving force. In very simple systems it's possible to excite only one "mode" or resonant frequency. In real world systems, many get excited at the same time. So you wind up with a complex dynamic motion of the muzzle. It's moving and deforming in 6 degrees of freedom - sideways, back to front, up and down, plus the three axes of rotation (roll, pitch, yaw). The precise orientation and motion of the muzzle as the bullet leaves determines the initial conditions for the bullets path.

Different charges will produce different velocities and drive the barrel vibration slightly differently (because it changes the driving force). When put all together, you can have the vibration cancel out the velocity variation. One of the predominant driving forces in a rifle is the imbalance in support and mass distribution in the vertical plane. Because of that, you get a large up/down component to the muzzle motion. That's why positive compensation is so easy to see relative to other barrel motion effects. It's not possible to calculate this motion precisely enough to be useful. Measuring it is extremely difficult and impractical. But we can see the effects on the target.

It's important to note that this is not all there is to what makes a load good. It's my belief/opinion that there is simply a great deal we do not understand. Some things we do, but we probably don't know more than we do. Some things we kind of understand but not well enough to be truly useful.

At the end of the day, we're rapidly approaching academics at this point. That's fine and I personally enjoy it for its own sake, but you don't need to understand how something works if you just want to print small groups. Knowing that it works is enough.

Damoncali: Thank you for your input!

For me it is harder to see a 6 DOF with a rifle barrel but more easily seen with the bullet. Often when talking about vibrational Nodes and or Modes I see no mention of balloting or the different bullet / bore interactions. Is balloting not just as important as barrel reactions with respect to a “good load”.

Your thoughts?

Thanks.

 

[dcali]

Damoncali: Thank you for your input!

For me it is harder to see a 6 DOF with a rifle barrel but more easily seen with the bullet. Often when talking about vibrational Nodes and or Modes I see no mention of balloting or the different bullet / bore interactions. Is balloting not just as important as barrel reactions with respect to a “good load”.

Your thoughts?

Thanks.

I'm getting out of my depth here, but I don't think balloting is a significant thing for small arms shooting match grade ammo out of match grade rifles. I was always under the impression that that was a concern for artillery the artillery guys. (Which I am very much not). I suppose you could have some balloting issues with some of the big ELR setups shooting solids, but again, not my area of experience.

I should qualify that with the fact that some tiny amount of balloting is of couse always present in real barrels, but I have no way to quantify its effects in small match grade barrels (and I haven't seen anyone else even try). I'd be surprised if it's significant, but who knows. Maybe there's a measurable effect.

Edit: There is an effect called lateral throwoff that is a close cousin of balloting- that is a thing, but not really related to barrel vibration - it's just the aerodynamic consequence of an off center bullet CG and the spin.

 

[K Hope]

I'm getting out of my depth here, but I don't think balloting is a significant thing for small arms shooting match grade ammo out of match grade rifles. I was always under the impression that that was a concern for artillery the artillery guys. (Which I am very much not). I suppose you could have some balloting issues with some of the big ELR setups shooting solids, but again, not my area of experience.

I should qualify that with the fact that some tiny amount of balloting is of couse always present in real barrels, but I have no way to quantify its effects in small match grade barrels (and I haven't seen anyone else even try). I'd be surprised if it's significant, but who knows. Maybe there's a measurable effect.

Edit: There is an effect called lateral throwoff that is a close cousin of balloting- that is a thing, but not really related to barrel vibration - it's just the aerodynamic consequence of an off center bullet CG and the spin.

Arrow Teck and J. Siewert have some interesting readings on bullet / bore interactions and small caliber dispersion. Topics including but not limited to: Early in-bore pressure induced clearances, lack of bore straightness (bullet lateral movement forces on barrel) and bullet concentricity; all contributing to bullet cross velocity and bullet angular rate.

Thanks!

 

[dcali]

Arrow Teck and J. Siewert have some interesting readings on bullet / bore interactions and small caliber dispersion. Topics including but not limited to: Early in-bore pressure induced clearances, lack of bore straightness (bullet lateral movement forces on barrel) and bullet concentricity; all contributing to bullet cross velocity and bullet angular rate.

Thanks!

Funny you mention that. I just got a copy of Siewert's book yesterday. Haven't had a change to look through it yet, but it looks interesting.

 

[ronsatspokane]

Anytime man. I'll give you another lesson on noodling your shots into the X ring next Sunday.

An update. So the young feller (the OP that is) noodled his way into the record books here in our local monthly F Class 600 yard match this morning. He cleaned all three strings with a very respectable X count using a new rifle in a new (to him) caliber. There have been a lot of top notch shooters with a lot of different calibers here over the years and no one can recall anyone over cleaning all three strings. The winds here can be very strange. Not hurricane force like Rattlesnake but subtle and difficult enough to read that they eventually catch even the best wind readers at some point.

Now I might have to try that caliber out myself. That kid is going to bankrupt me trying to keep up with him. Oh well, can't take it with you.

 

[cwood59]

Funny you mention that. I just got a copy of Siewert's book yesterday. Haven't had a change to look through it yet, but it looks interesting.

I mentioned before, the book is worth the read. Also, his appearances on the "Hornady Manufacturing" YouTube channel are very enlightening.

 

[praveen]

An update. So the young feller (the OP that is) noodled his way into the record books here in our local monthly F Class 600 yard match this morning. He cleaned all three strings with a very respectable X count using a new rifle in a new (to him) caliber. There have been a lot of top notch shooters with a lot of different calibers here over the years and no one can recall anyone over cleaning all three strings. The winds here can be very strange. Not hurricane force like Rattlesnake but subtle and difficult enough to read that they eventually catch even the best wind readers at some point.

Now I might have to try that caliber out myself. That kid is going to bankrupt me trying to keep up with him. Oh well, can't take it with you.

Frankly, it was one of the most, for lack of a better word, uncomfortable, cleans I've shot. It needs more load development and some of the things said on this thread should help me with it.