Accuracy Node Spacing

[old303]

I'm looking at a ladder test I did at 0.5-grain spacing over a 4-grain range (9 groups) and seeing one near the middle I really like, but I'm wondering if I should try splitting some of the gaps and fishing for a node between any of the slightly larger groups, especially as I'd like a bit more velocity. For those of you who have found more than one node for a rifle/bullet/powder combination, how many grains apart do they tend to be?

6.5 CM with 140 grain bullets and N555 here, but I'm wondering if there's any rule-of-thumb that fits most precision calibers.

 

[adamg]

A) I'm not convinced that "nodes" exist,
B) Those are massive powder charge steps between tests,
C) Either your coldest loads are way too slow to be useful or your hottest loads are way too hot to be comfortable with such a wide spread, and
D) You didn't mention if this "node" is looking better as measured by group size or velocity spread.

 

[titch--]

3% is what Ive read/seen

 

[old303]

This was with a new-to-me powder, with manufacturer load data available, and I was being responsible and starting at the start value and working up toward the max and watching for any pressure sign, so taking decent strides up the whole range they recommend. And I had some loose groups early and late in the series, but a couple of good ones near the middle.

I'm sure there are people who would go straight to the max charge then start violating that from there, but that's not how I got to my present age with all fingers and toes still attached.

I was expecting another test cycle in 0.1 grain intervals, but wanted to glean as much wisdom as I could from that first session to strategize where to zero in for the next and not waste any range trips.

So if it's a slow cycle there would have only been that one node and I'd have to refine there and be happy with less velocity, but a 3% ratio cycle suggests it's worth splitting the top end of the range in finer increments and there could be a couple of good points above the one I saw, and predicts where to start looking. Thanks!

 

[Big bore dinosaur]

I prefer the bottom end of the node..
As the barrel warms, the speed increases.

 

[358Rooster]

Just my 2 cents for whatever you find it's worth...
In a Creed size case, if I were looking strictly for my pressure ceiling, I might use 1/2 grain steps. Now saying that, a 1/2 grain above one shot that might be on the ragged edge of pressure without showing obvious signs yet, might put you over the top by a reasonably considerable amount. Possibly...

But for typical initial load development where you're looking for rough stabilities in velocities as well as precision, 0.3 grain steps in a Creed size case is more appropriate, in my opinion. Once you can pick out a couple (or three) groups that show some stability exhibiting very similar group size and position, knock the charge increments down to 0.2 to refine around that area of stability and go to work again. 0.1 grain increments MAY be useful, but I personally feel that's more for BR competitors and guys who just love to test

Regarding node-to-node gaps, I have noticed about 1.3 grains in Creed & 260 Rem testing, but they're certainly not super predictable. Smaller cartridges tend to have smaller gaps, bigger ones tend to have bigger gaps, to a point. Part of me believes this variability has a lot to do with powder / bore ratio. That is simply my anecdotal observations and I haven't put a great deal of effort into 'sciencing' that one.

I'm very much with Adamg on the node thing: I'm not convinced that so-called nodes are as solid a data point as a lot of us would like to believe, but I currently have no other way to explain those convenient small spreads of data that seem to line up together. My trouble with continued belief in nodes is that there is almost always a decent amount of statistical noise surrounding them. I think for the most part, we find some comfort in the belief that we have hit a node and we'll ride that train until it stops.

Bit of a departure from the original query, so I'll stop there. old303 let us know how you make out.

Rooster

 

[PGW Steve]

As Adamg and 358Rooster mention about 'nodes' being bad information, I agree. The whole concept of running a whole bunch of incremental powder steps and picking a load based on a few of the velocities showing a 'node', is the biggest scam the shooting community has bought into. Everyone is chasing low ES and SD's should know that shot to shot velocity varies. To think that there are no variances in a string and that the nodes are hard data is believing a big lie. Shot 1 velocity is say high, within the accepted ES range. Shot 2 velocity is say average of this range. Shot 3 is low in the ES spread. Now you have 3 velocities that are essentially identical, but are nothing more than random, accepted statistics. Somehow they're now seen as a 'node' and that is what the gun is supposed to like. BS.

The method I've been using for 30 years is simple. Go to the range with prepped and primed brass. A powder measure with graduations like a micrometer, a chart of settings for your powder, and your press to seat bullets. Start low, fire a single shot, check velocity and pressure. Keep moving up while watching velocity and pressure, single shot at a time. When you start getting into the "I'm happy with the speed" range, start with 3 shot groups. Keep moving up with 3 shot groups until you find a speed/accuracy that works. Now mess with seating depths, and not .003" at a time. Do .020" jumps and see what the rifle likes. So many people shoot out a barrel chasing 1/4 moa groups. Unless you're shooting BR, be happy with 1/2moa. Save your barrel life and components for long distance and windy practice, that is where the differences are, not in 1/4moa at 100.

 

[sonichanxiao]

Most people I know increasing the charge by 0.2 or 0.3gr, but you need to load more than 1 round per charge to get an average speed.

Or you could ignore the speed change when increase the charge, instead, look for group patterns.

 

[old303]

I tried the likeliest gaps in my earlier ladder, found sloppy groups in two, but lovely tight sub-MOA in the third (and fastest!) one so that's what I'll run with. And that was with 10 rounds so better statistical confidence.

I may still go back and try 0.1 gr increments and also get closer to the lands, but I'm quite happy for now.

Loading onsite with pre-primed brass is attractive, then I can follow findings on the same visit. I can't bolt a full-sized press into the club's shooting bench, but a portable press would work. Some protection from the sun and breeze would be in order (especially from wind upsetting powder measurement). Halfway tempted to look into a portable power bank that can run the Chargemaster!

Also thinking it might be wiser to try 0.8 gr or 0.4 gr increments from the starting load, probably big strides low and small strides as I approach max, so that splitting in two works better. With an initial survey in 0.5 gr increments, you have to decide whether to go up 0.2 or 0.3.

And I'm not that concerned with ES and SD, they may be useful as diagnostic indicators, but how tight a group the ammo makes downrange is the true measure of it.

 

[wallz]

For the 6.5 cr I use 0.2 gr increments, and usually automatically drop the lower 30% of the "safe" range the manufacturers suggest, and sometimes go above the suggested. Yea I know, my own risk, but I have found nice groupings above "max" loads in one book, and they were still under "max" loads in another, so take those all with a grain of salt, and see what your combination likes.

I am more interested in the top 20% safe range, and there usually find a good combination that the rifle likes, and I sometimes don't even hit the "ceiling" of max in my tests, and sometimes have to stop early when reaching signs I'm comfortable with knowing I'm getting close to top end pressure.

I did try N555 in my rifle and didn't like the speeds of the better groupings, so moved on from that powder. Not saying yours won't like it, just slower than I liked.

I tested my setup with continuous strings, and I know that when the barrel heats us, I want that accuracy, not necessarily on my first shot, but its not a hunting rifle either, so that matters. Once I find my combination, I usually run a 10 shot sting to verify and set things. For a hunting rifle, I'll usually go 5 shots.

Don't even bother with fine tuning unless you are past that 100 shot mark in the barrel, and once shot brass. New brass, and new barrels will perform differently.

 

[Lead hammer]

I like .3 for powder, 0.003” seating. Then confirm it all at 300meters. Sometimes it needs .1 more or less powder at 300 m based on the confirmation groups. 10 shots. I use OCW and OSD. If the load shoots, the ES will be decent. If choosing loads only off ES/SD, you can be way off.

 

[m1008]

Didn’t Hornady do a few podcast disproving “nodes”

Why don’t you guys shoot some 30 round groups?

 

[adamg]

Didn’t Hornady do a few podcast disproving “nodes”

Why don’t you guys shoot some 30 round groups?

Unfortunately for them and us, their technique has not demonstrated itself superior by winning a big accuracy match - much less all of them.

 

[Lead hammer]

I for one think both Hornady and one other individual are stuck in stats. Top shooters are always adjusting loads on the fly and use previous barrel and load history to get repeatable results. The need to adjust load or tune to survive the mornings and stay in tune in the afternoon are things that Hornady does not do in testing. One top F class shooter can even find a sin wave with one fired round at each powder charge. I certainly am not good enough to do that, and frankly that method would not work for me, and is why I do OCW.

 

[358Rooster]

Not to mention that Hornady's resources are far beyond what I'm sure most of us could only dream of. Hell, I'd shoot 30 round groups (or more) every damn day if I had even remotely close to the same assets they have.

Unfortunately for them and us, their technique has not demonstrated itself superior by winning a big accuracy match - much less all of them.

 

[iron cat]

I have found that many hand loaders chasing accuracy at our range tend to concentrate on the wrong things at times, nodes being one of them .
Trying to find an accuracy node with a particular powder charge is fine, but trying to get a rifle to shoot sub 1/2 inch groups at 200 meters with a rig that is not really capable, a shooter who cannot replicate said groups because of their expertise, or hand loading equipment tgat is not absolute top shelf is a fool's errand.
To top it all off, many of the rifles I see being used are hunting rifles for big game, and if a person believes they need a 200 meter 1/2" capable rifle to kill a deer at 300 meters, well, they are chasing rainbows.
Cat

 

[358Rooster]

Yep, I agree. Although there's nothing wrong with chasing rainbows, acknowledging the realistic limitations of everything that Iron Cat has stated above is often where most of us fall on our faces. Needs and desires are two different things.

Dare to dream, Billy. Dare to dream...

 

[iron cat]

Yep, I agree. Although there's nothing wrong with chasing rainbows, acknowledging the realistic limitations of everything that Iron Cat has stated above is often where most of us fall on our faces. Needs and desires are two different things.

Dare to dream, Billy. Dare to dream...

Believe me when I say I too can get stuck on a particular thing as far as accuracy goes, and forget something.
This usually gets pointed out by someone else as opposed to myself having an epiphany! LOL
Cat

 

[jimbo14]

I like stats like Litz and others, and I have seen comments about nodes not really existing if your sample size is large enough. I used to go by velocity alone and look for flat spots, and have since learned that’s bunk.

However, I primarily shoot on a bench, with a rear bag, and my main range is only 100m. So lately I’ve been doing OCW and shooting 3-shot groups, round robin, from low charge to high, high to low, then low to high again.

Then looking for the elevation shift in each 3-round group and identifying nodes where the average elevation of adjacent groups are similar.

I’m starting with a good mechanical baseline. 6GT, 26” MTU barrel, heavy ACC chassis, 10-ounce trigger, powder charges using FX-120i scale, etc. Sightron 50x scope at 100m with a rear bag in zero or near zero wind, helps reduce aiming errors.

Doing this, I can see a sine wave in my groups as I go from low charge to high charge. The regions that are supposed to give more consistent groups will align with the peaks and valleys of the sine wave.

Between these regions, I believe the inventor of OCW called these areas of larger groups, ‘scatter nodes’, and +/- about 1.5% charge weight should get you to the next peak or valley.

I’ve seen different +/- % values, but one of these days I’ll do a test and load up a bunch of my good load and a bunch of the ‘scatter node’ groups, and see how they shoot. Maybe 30-round groups of each, round robin style.

 

[Lead hammer]

I like stats like Litz and others, and I have seen comments about nodes not really existing if your sample size is large enough. I used to go by velocity alone and look for flat spots, and have since learned that’s bunk.

However, I primarily shoot on a bench, with a rear bag, and my main range is only 100m. So lately I’ve been doing OCW and shooting 3-shot groups, round robin, from low charge to high, high to low, then low to high again.

Then looking for the elevation shift in each 3-round group and identifying nodes where the average elevation of adjacent groups are similar.

I’m starting with a good mechanical baseline. 6GT, 26” MTU barrel, heavy ACC chassis, 10-ounce trigger, powder charges using FX-120i scale, etc. Sightron 50x scope at 100m with a rear bag in zero or near zero wind, helps reduce aiming errors.

Doing this, I can see a sine wave in my groups as I go from low charge to high charge. The regions that are supposed to give more consistent groups will align with the peaks and valleys of the sine wave.

Between these regions, I believe the inventor of OCW called these areas of larger groups, ‘scatter nodes’, and +/- about 1.5% charge weight should get you to the next peak or valley.

I’ve seen different +/- % values, but one of these days I’ll do a test and load up a bunch of my good load and a bunch of the ‘scatter node’ groups, and see how they shoot. Maybe 30-round groups of each, round robin style.

3 shot groups for detection elevation shift works good, and is what I do also. Many people are using the sin wave to include positive compensation. I’m not going there ( just want a middle “node”, until I get a new barrel, and a new trigger.