Nodes explained

Bmoore0062

Bmoore0062

Sergeant of the Hide
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Sep 30, 2018
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#1
So feel free to re-direct me to an existing thread if it exists. I did use the search function, didn’t find what I was looking for.

I would consider myself a novice reloaded. Around about 3 years of reloading but just getting into Precision shooting.

Just looking for feedback on finding the right node? Hell what is a node?

Right now I am loading for 308 for a RPR with an LRI Barrel. 42.6 gr of varget, coal of 2.82” and averaging about 2575fps. Shooting 175gr nosler RDF bullets with lapua brass. I believe I’m loading about .005” of the lands. If my memory serves me well, data is in my book in the basement. Bolt is not too loose or too tight. No signs of pressure etc.

I would say I am averaging probably about .85 MOA to 1 MOA.

I did some ladder test to get to the load I am at but was really just looking at groups. I did chrono each to look at speed but honestly went with what group the best. Is there more to find the right node and the right load?

Would you all be happy with this performance? I personally shot better groups consistently with factory 175 federal gold medal match. Average about .65 -.7 MOA. Which that bullet has a lower BC than the nosler.

Thanks in advance.
 
#5
Research. You are obviously one that would benefit from it. Once you know how everything works you will know why you are doing what you are doing. Without that you can try other guys loads for ever and just go in circles. Find clto for rifle. Ladder test. Find pressure mode. Adjust coal. Repeat with different powders and bullets until happy or time for a new barrel.
 
#6
A "node" is a load that shoots well across some range of charge weights.

It is a combination of charge weight, seating depth and barrel timing. The idea being, to pick a powder charge that is safe, but within the optimal pressure range, and a seating depth that optimizes barrel timing so that the bullet is leaving the barrel at the point where it is changing direction in the harmonic pattern.
 
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#7
I don't know much about RDFs, but if you're just getting into precision loading, I'd pick a bullet that isn't extra-sensitive to seating depth. Then all you really need to vary is the charge weight to get started as long as you have good brass and primer and a powder that isn't temp sensitive.

Or you can start with something that is jump sensitive and just get input from others on what type of jump usually shoots well with that bullet. It's unlikely you'd be too far off as long as you start close to a known good area.
 
#8
The nosler RDFs actually perform really well when you load them 0.030-0.040 from lands. 3 different calibers ( 6.5, 6mm and 308) all did the same. I use 0.020 as my defacto starting for load development and best I got from them was around 0.75 MOA and almost said screw it. Then I tried the seating depths and low and behold....pushed them in a bit and they shrunk to a respectable 0.5MOA with a best showing 0.35 ( I didn't shoot it but I have something to strive to)
 
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#9
Sorry, but you asked a question that would take pages to answer properly. The short answer:

NODE (Accuracy Node) - it is the range of powder charges that produce the best group(s). You fire the following charges, with the following results (purely hypothetical):
42.0 Grains - 1.2" Group
42.2 Grains - 1.0" Group
42.4 Grains - 0.8" Group
42.6 Grains - 0.8" Group
42.8 Grains - 1.0" Group
43.0 Grains - 1.2" Group
Your Accuracy Node would be 42.4-42.6 Grains, because those powder weight charges produce the best group(s). Somewhere in that Node, there will probably be a single powder charge weight that will give you the best results.

You can also look at Nodes in terms of Muzzle Velocity, picking the powder charge weight(s) that give you the smallest deviation. Ideally you would like to find something that has an extreme spread of less than 10-15 fps.

A Node is basically the "Sweet Spot" where the rifle is shooting the best. This has to do with how the load and the rifle are interacting, specifically how that powder charge interacts with the barrel.

All barrels whip and move:


There are also harmonics involved:
https://www.youtube.com/results?search_query=barrel+harmonics

In really simple terms, the Node is the point where the bullet exits the barrel under the best possible conditions. It is in the center/most stable part of the barrel movement and vibration. With some rifle barrels (high quality, rigid, etc) this Node or Sweet Spot can be fairly wide, with others (low quality, thin, stress, etc) the Node can be very small.

This is purely a function of timing, which comes down to muzzle velocity, which comes down to powder charge weights. Some barrels may have a fairly large sweet spot that may be 15-20 fps, which could equate to 3-4 tenths of powder charge weight. Some barrels may have a very small sweet spot that is 5-10 fps, which could equate to 1 or 2 tenths.

Sorry for the short explanation, hopefully it helps, if you have questions, fire away.
 
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#10
A node is not a sweet spot. It is a fork in the road. They say it don't be like it is, but it do. Load to touching the lands. Not jammed. Load in increments until you first start seeing pressure signs. Back off .5 gr. It is a 308 and not some overbore. Enjoy reloading and shooting your rifle.
 
#11
https://www.sniperforums.com/forum/reloading/43364-308-reloading-data-only.html

Third post down is Dan Newberry with the OCW test and website.

I've shot the 175 RDF in a factory AI barrel, Bartlein AI barrel, Rem 700 16.5" barrel, and my buddy has experience with them in a Bartlein AI barrel and Rem 700 20" barrel.
The nodes you seek are higher and with more jump.

43.0 to 43.5 and 44.5 to 45.0 grains of Varget in Lapua brass is the tits with a 175 grain bullet.
0.060" to 0.090" off the lands is the area to strive for.

I've had them group under 1/4" at 100 for 3 shots with 44.4 Varget and jumping 0.180"....that's not a typo, 0.180" off the lands.
I've even got a subsonic load for them that drops 5 into 3/4 MOA at 200 yards with 34 ES and 13 SD for 7 shots...at 0.210" off the lands.
The RDF is not a jump sensitive bullet.
Back that bullet off the lands.
 
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#13
Supersubes said:
http://optimalchargeweight.embarqspace.com/

Seem to recall most people jumping the RDF’s, and also quite a few just couldnt get them to group. Either way, no need to load so close to the lands.
Click to expand...
OP, just follow this link, ignore the rest until you can sort through the bullshit.


Skookum said:
A "node" is a load that shoots well across some range of charge weights.

It is a combination of charge weight, seating depth and barrel timing. The idea being, to pick a powder charge that is safe, but within the optimal pressure range, and a seating depth that optimizes barrel timing so that the bullet is leaving the barrel at the point where it is changing direction in the harmonic pattern.
Click to expand...
This is the essence of what we are looking for.


We arent looking for the best groups right off the bat like someone above said (its hypothetical because its wrong), we are looking for a spot where the point of impact doesnt shift with a tenth or two of charge difference. Once you find that charge area you adjust the seating depth to time the bullets exit.


As far as any specific jump with the rdfs, I think it ranges a fair amount and probably just as much due to the people employing their different measuring technique, chamber and tools. My 70 rdfs were .060, my 105s are .015 off.
 
#15
bfglowkey said:
The nosler RDFs actually perform really well when you load them 0.030-0.040 from lands. 3 different calibers ( 6.5, 6mm and 308) all did the same. I use 0.020 as my defacto starting for load development and best I got from them was around 0.75 MOA and almost said screw it. Then I tried the seating depths and low and behold....pushed them in a bit and they shrunk to a respectable 0.5MOA with a best showing 0.35 ( I didn't shoot it but I have something to strive to)
Click to expand...
Thanks I will give that a shot. Literally....
 
#16
Skookum said:
A "node" is a load that shoots well across some range of charge weights.

It is a combination of charge weight, seating depth and barrel timing. The idea being, to pick a powder charge that is safe, but within the optimal pressure range, and a seating depth that optimizes barrel timing so that the bullet is leaving the barrel at the point where it is changing direction in the harmonic pattern.
Click to expand...

Thanks for the explanation on the term. Was a bit curious. But makes sense. I was overthinking it back to math class with nodes and graphs, etc.... thinking this involved some type of formula/equation and crap.
 
#18
spife7980 said:
OP, just follow this link, ignore the rest until you can sort through the bullshit.



This is the essence of what we are looking for.


We arent looking for the best groups right off the bat like someone above said (its hypothetical because its wrong), we are looking for a spot where the point of impact doesnt shift with a tenth or two of charge difference. Once you find that charge area you adjust the seating depth to time the bullets exit.


As far as any specific jump with the rdfs, I think it ranges a fair amount and probably just as much due to the people employing their different measuring technique, chamber and tools. My 70 rdfs were .060, my 105s are .015 off.
Click to expand...

Thanks for the link and info. I will be sure to check it out.

Before I get butchered alived, I know my coal is 2.82”. I don’t recall how far off I am from my lands. I will remeasure and bump it back.

On related note I have heard some people say with heavier bullets in 308. They can take longer to stabilize and group better at 200 yards vs. 100 yards. I have shot paper at 100 but not at 200 to verify. All and all still decently satisfied. I have taken this load out to 1000 yards on three occasions. I was consistently ringing an 8x8” plate. Just want to chase it and see if I can get a tighter grouping.
 
#19
Ignore the bullets going to sleep at distance theories, its not something to concern yourself with and Litz has a standing offer to pay something or other to anyone who can prove its existence, no one has yet. Some weird stability things can be observed but not the going to sleep thing.


There is something to be said about positive compensation, the barrels do move like the graphs you are thinking of, sine waves, but its not just along one axis, its along all axis. Tuning for positive compensation at distance basically means that the slow bullets are coming out of the bore when the barrel is on its up swing and that the fast ones are coming out on the down swing so that at a certain distance those meet up for a nice group.
positive_compensation.jpg





OCW, like subes link above describes, is looking at all of those vibrations and where they meet at a nice harmonious spot on paper.
aussiehunter-concept-of-OCW-load-method.jpg


Ladder testing tries to stick to the same underlying theory but it is done at distance and focuses mainly on the vertical aspect at distance.
baneylad00.png




All said a load that will hit a 8x8 plate at 1k consistently is doing pretty damn well already.
 
#20
spife7980 said:
Ignore the bullets going to sleep at distance theories, its not something to concern yourself with and Litz has a standing offer to pay something or other to anyone who can prove its existence, no one has yet. Some weird stability things can be observed but not the going to sleep thing.


There is something to be said about positive compensation, the barrels do move like the graphs you are thinking of, sine waves, but its not just along one axis, its along all axis. Tuning for positive compensation at distance basically means that the slow bullets are coming out of the bore when the barrel is on its up swing and that the fast ones are coming out on the down swing so that at a certain distance those meet up for a nice group.
positive_compensation.jpg





OCW, like subes link above describes, is looking at all of those vibrations and where they meet at a nice harmonious spot on paper.
aussiehunter-concept-of-OCW-load-method.jpg


Ladder testing tries to stick to the same underlying theory but it is done at distance and focuses mainly on the vertical aspect at distance.
baneylad00.png




All said a load that will hit a 8x8 plate at 1k consistently is doing pretty damn well already.
Click to expand...

Thanks for the clarity makes a lot more sense. I have read Ryan Cleckners book and reading one of Brian Litz book’s. The more I read on the topic of long range shooting, the more I realize I don’t know.

As far the 8x8” is concerned last time I went out I was 4/5 on it. Danced all around the edges of the 4x6” target. Time before that I shot at that distance there were some tricky winds. It was not as easy. Reading wind is something I defiantly working on as well.
 
#21
This is a fun topic - here is my $0.02. Bow to Mr. Culpepper, feel free to ignore this note too.

When the round fires, it creates a shock wave - think of whacking the barrel with a hammer - that bounces around inside the barrel. The shock wave moves through steel at about 5700 meters per second - maybe 18,000 feet per second. So the shock wave starts at the chamber but reaches the muzzle a lot sooner than the bullet does. All of this energy bouncing around inside the barrel deforms it. The barrel twists and untwists, gets shorter and longer, and whips back and forth, up and down, wriggles like a snake - all kinds of motions. I was trying to come up with a stripper metaphor -- think about what you would see for $100 -- but I will leave that right there.

So let's choose one motion - muzzle pointing right then left then right and so forth. Initial condition: the muzzle is pointing center and moving to the right. It slows, then slows some more, then stops moving right. Then starts to slowly move to the left, faster, faster, passes through center, starts to slow down, slows, stops at the left limit and the cycle repeats. If you can make the bullet emerge from the barrel when it is stopped either right or left, the barrel will always point to the same spot and you will get a small group and that is a "node".

Note that small changes in timing will find the barrel pointing pretty close to the same spot so there is an ideal combination but a good node shoots into a small group across 0.2 or 0.3 or more grains of powder range and with minor seating depth variations. This is in your favor because you can make small measurement mistakes without screwing up your groups.

Three comments:

First, the barrel motion is not nearly that simple.

Second, you don't want to try to find a node in the center because that is the time when the barrel is deflecting the fastest. It doesn't stop deflecting in the middle, it stops deflecting at the ends.

Third, you aren't looking for the group farthest right or left. You are looking for three different powder charges that landed in about the same place.

You control the timing with powder charge, primer, bullet, seating depth, and temperature. There are some known good 308 loads that work in most guns but every barrel is a little different so you may have to fiddle around a little.

You mentioned math class - think about solving several simultaneous partial differential equations, mostly X and Y with respect to time. I could not do that work to save my ass but I don't have to. The gun is my computer, it figures it all out for me. All I have to do it feed it different kinds of ammo and let it throw bullets.

Again, feel free to ignore me. This is just how I think about it, maybe it will help you, maybe not.
 
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#23
bax said:
Three comments:

First, the barrel motion is not nearly that simple.

Second, you don't want to try to find a node in the center because that is the time when the barrel is deflecting the fastest. It doesn't stop deflecting in the middle, it stops deflecting at the ends.

Third, you aren't looking for the group farthest right or left. You are looking for three different powder charges that landed in about the same place.

You control the timing with powder charge, primer, bullet, seating depth, and temperature. There are some known good 308 loads that work in most guns but every barrel is a little different so you may have to fiddle around a little.

You mentioned math class - think about solving several simultaneous partial differential equations, mostly X and Y with respect to time. I could not do that work to save my ass but I don't have to. The gun is my computer, it figures it all out for me. All I have to do it feed it different kinds of ammo and let it throw bullets.

Again, feel free to ignore me. This is just how I think about it, maybe it will help you, maybe not.
Click to expand...
Here is a link with illustrations:

http://www.varmintal.com/amode.htm
 
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#27
Skookum said:
Here is a link with illustrations:

http://www.varmintal.com/amode.htm
Click to expand...

I remember seeing those picture somewhere before this. Really nice visualization for what I was trying to say! I hadn't thought about the "plucking the string" idea. I need to contemplate that some more - or maybe not :) Thanks for posting that.
 
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#28
Bmoore0062 said:
So feel free to re-direct me to an existing thread if it exists. I did use the search function, didn’t find what I was looking for.

I would consider myself a novice reloaded. Around about 3 years of reloading but just getting into Precision shooting.

Just looking for feedback on finding the right node? Hell what is a node?

Right now I am loading for 308 for a RPR with an LRI Barrel. 42.6 gr of varget, coal of 2.82” and averaging about 2575fps. Shooting 175gr nosler RDF bullets with lapua brass. I believe I’m loading about .005” of the lands. If my memory serves me well, data is in my book in the basement. Bolt is not too loose or too tight. No signs of pressure etc.

I would say I am averaging probably about .85 MOA to 1 MOA.

I did some ladder test to get to the load I am at but was really just looking at groups. I did chrono each to look at speed but honestly went with what group the best. Is there more to find the right node and the right load?

Would you all be happy with this performance? I personally shot better groups consistently with factory 175 federal gold medal match. Average about .65 -.7 MOA. Which that bullet has a lower BC than the nosler.

Thanks in advance.
Click to expand...
Look for Scott satterlee’s post or in 6.5 guys website.
 
#29
Brandon05_88 said:
https://www.sniperforums.com/forum/reloading/43364-308-reloading-data-only.html

Third post down is Dan Newberry with the OCW test and website.

I've shot the 175 RDF in a factory AI barrel, Bartlein AI barrel, Rem 700 16.5" barrel, and my buddy has experience with them in a Bartlein AI barrel and Rem 700 20" barrel.
The nodes you seek are higher and with more jump.

43.0 to 43.5 and 44.5 to 45.0 grains of Varget in Lapua brass is the tits with a 175 grain bullet.
0.060" to 0.090" off the lands is the area to strive for.

I've had them group under 1/4" at 100 for 3 shots with 44.4 Varget and jumping 0.180"....that's not a typo, 0.180" off the lands.
I've even got a subsonic load for them that drops 5 into 3/4 MOA at 200 yards with 34 ES and 13 SD for 7 shots...at 0.210" off the lands.
The RDF is not a jump sensitive bullet.
Back that bullet off the lands.
Click to expand...
Thanks for the info!
 
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