interesting load dev question: how do you know roughly where the nodes are?

[Whiterabbit]

Let me explain the question.

So, we know (this is the fact, if you disagree speak up or else the rest will make no sense) that we consider most rifles to have a few "nodes" of accuracy such that we can shoot accurate reduced loads when desired.

OR, put another way, we know from the idea of ladder testing that we expect a range of charge weights to eventually be insensitive to elevation changes. Sinusoidal in performance, which plays well into the idea of accuracy "nodes".

So, if that is the "fact", then my question is this: If I do not have easy access to 300 yards, and I want to bracket a single node, how to go about doing that? I do not need to nail the node, I'm looking for a way to know, with reasonable confidence, that a minimum and maximum charge will contain exactly one accuracy node, and not cross over into the next region of the "sine wave" (so to speak).

I imagine it would be easy via ladder test to accomplish this. But how to do it at 100 yards with a minimum of bullets?

Ideas?

[McGuiver]

interesting load dev question: how do you know roughly where the nodes are?

Caliber? Bullet type? Bullet weight? Powder? Barrel length? Twist rate? Gun model?

All these would help with your decision on finding nodes. A SBR 10" AR in 223 with a 1 in 7 twist rate throwing a 35 gr bullet will have a different node then a 55gr bullet and so on.

For my pistols, to find the nodes for accuracy for a given powder I usually load from min to max loads. Only upping the powder charge .1 grains every 10 rounds. I load 10 rounds per segment then up it another .1 grains. This allows me to shoot 2x 5 shot groups to verify data and to rule out fliers and a unsteady hand. I will be starting here this week to do the same thing for my rifle in 223. I'm just OCD. you could up it by .2 grains for a rifle load. Finding nodes cost money.


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[Whiterabbit]

Good question! This would be general bolt rifle. Any answer should be universal and not require cartridge, caliber, twist rate, etc. Since for example, general ladder type load dev, OCW, etc are all universal and do not require inputs based on cal and cartridge.

DOES require the specification of rifle though, if that was not obvious up front.

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To be clear again:

The question is NOT about "finding the node", it's about bracketing the node.

[Whiterabbit]

hrm, I think I got it.

The internet suggests I can accomplish the same thing using the chronograph instead of vertical dispersion.

[760practicalshooter]

Like above, ladder-load in charge weight increments. Shoot groups, find most consistent and tightest groups. Reload and fine tune in that sector of powder charge for best load data.

[Unretarded]

Going out tomorrow, min towards max........10 rounds per load in .5 increases, not sure there is a shortcut.

I like shooting, so 200 rounds plinking or testing is still shooting.

Maybe I will get lucky and get close on one and another session will get me on base.......of course this application is long distance, so crono readings tests at different distances also have to happen.

Depends on how far down the rabbit hole you want to go and what you are doing.....if you are going all the way down the rabbit hole some say the barrel is shot out by the time you really get it dialed in and the process starts over.

A better question would be does load development ever stop, my answer would be when you get close as makes you happy, because a new batch of bullets and keg of powder changes things some also.

I think once you go all the way you just load batches as consistent as possible and run with it as the next batch of bullets,powder,brass changes things again.

[Whiterabbit]

Well Unretarded, let's play with your test, I think it's a great start.

Let's say we want to go the route of 10 rounds per load in .5 grain increments. Sounds like a great way to get gross data before fine tune.

How do you determine where the stable regions are? since you say load up 10 rounds per, are you just shooting for groups and evaluating statistics on group size alone?

Seems effective, but requires a huge number of rounds. As you suggest, a 5 grain spread to narrow the field is 200 expensive bullets! Plus, what happens when you discover your ideal range across, say, 1.5 grains of charge weight? that suggests that you've shot ALOT of rounds outside the range you are looking at fine tuning in?

Seems like it all hinges on the idea that shooting is enjoyment no matter what is a joy. Hard to disagree with that but I can't help but wonder if alternative methods are more efficient getting you to the fine-tune range?

[LynnJr]

WhiteRabbit
You can find nodes with a chronograph but most shooters don't use there chronographs correctly.
Your shots need to be spaced out evenly in order to get accurate results. If you shoot two to three rounds in 30 seconds then let the 4th round cook off in the chamber your numbers will be all askew.

[Whiterabbit]

The problem statement is understood. If I space out the shots say, 5 min intervals, would you agree chamber heat is a non issue? rough estimate @ 5 min of course.

[LynnJr]

Whiterabbit
When your checking for velocity and extreme Spread you just need your rounds spaced out evenly and once the round is chambered you don't want any hesitation in firing.
I see guys at the range shooting across a chronograph and they shoot two rounds spaced about 1 minute apart.
They put the 3rd round in the gun close the bolt and look through the scope for two minutes before firing.
You will never get good results letting a round cook in the chamber.

[Unretarded]

Whiterabbit
When your checking for velocity and extreme Spread you just need your rounds spaced out evenly and once the round is chambered you don't want any hesitation.
I see guys at the range shooting across a chronograph and they shoot two rounds spaced about 1 minute apart.
They put the 3rd round in the gun close the bolt and look through the scope for two minutes before firing.
You will never get good results letting a round cook in the chamber.

Well where was this answer before I just spent all day shooting rounds over a magnetospeed....lol/JK.

I knew enuff to keep up a consistent pace, but that info would have allowed me to get a little better data, still happy with what I did get.

I will put that to use next time !

[Whiterabbit]

Basically telling me to ignore barrel heat when running chrono data. Cool.

[Odd_Ball]

Whiterabbit
When your checking for velocity and extreme Spread you just need your rounds spaced out evenly and once the round is chambered you don't want any hesitation in firing.
I see guys at the range shooting across a chronograph and they shoot two rounds spaced about 1 minute apart.
They put the 3rd round in the gun close the bolt and look through the scope for two minutes before firing.
You will never get good results letting a round cook in the chamber.

Can I assume the same applies if developing a load for a semi-auto rifle, like an AR-15? As in load a single round in the magazine, chamber round then fire, remove and reload magazine with a single round, and chamber round then fire at minute 1, 2, etc.? Or am I over thinking it?

I have to admit that for 45acp in my 1911, I didn't really think about this. I just loaded each set of 5 rounds in the magazine and fired them off, not rapidly but not waiting either once the sights were back on target. (I was not using a chrono.)

[Unretarded]

Let me preface my reply by saying I know nothing.

I have gotten by over the years with a healthy dose of common sense and logic......sometimes I win and sometimes not.

I have no idea if what I did was correct or not.

I ran the crono under my normal shooting conditions....seemed logical in this application.

I usually shoot a fair amount per session, approx 500 rounds 223. I do not clean during a session in this rifle.

I shot approx 100 rounds at my normal rate of fire to get up to operating temp and fouling level.

I then shot 10 rounds of each ammo tested at a consistent rate of approx 3 to 5 seconds apart.

Seemed like the right thing to do, could of been the worst possible way ?

This was a Ar-15.

[Whiterabbit]

Question for Lynn:

First, I totally get your statement. Let the cartridge heat up and the temperature dependence of the powder will affect the chrono result. OK.

Now, it just occurred to me that barrel heat should have a major effect on chrono data too, yes? As the barrel heats, it's gonna expand, even a sub cal might expand enough to see a friction change in the barrel, maybe even .001" in the chamber? Enough to affect expansion volume in the chamber and friction of hte bullet moving down the bore? (affect enough to see in the chronograph that is)

Or is it cool to just start cold bore and "rapid fire" through the shots to get my data, so the first rounds are cold bore and the last are raging hot? Just so long as dwell time in the chamber is short?