Barrel harmonics and reloading discussion

[Ryridesmotox]

I'm not sure how into the weeds everyone gets with reloading. That said, this week me and a friend were contemplating reloading and our different positions on it. Also, if this thread is better in another area, let me know so I can delete it and move it there.

He prefers a lower speed accuracy node because it is more accurate and arguably easier to tune. I prefer a higher speed accuracy node because I shoot 308, and I want to run as fast as possible to cheat wind at least in my eyes.

When contemplating these two different positions, I wondered why the higher speed node is narrower and more picky. Is it because barrel harmonics? IE, the barrel vibration is higher frequency or something like that.

The reason he and I were discussing this was because I recently was doing an OCW test. During that test, in my higher speed load, I went from 45.4gr and about a 1moa group to 45.6gr and less than .5 moa, back to 1 moa at 45.8gr. I was hypothesizing that the. barrel is vibrating faster which allows for less of a node... either that or my group and results were complete luck, which is also 100% possible.

What do you guys think? This is just for hypothetical or academic purposes on the subject.

 

[Backcountryguy]

Can’t answer your specific question on the harmonics, but a chronograph can/will solve the question node.

I find a charge weight with low SD/ES first, and during this stage I don’t worry about groups, I usually shoot at steel. After finding a charge weight with low SD/ES, I do a seating depth test. Tightest groups wins the development. Confirm the SD/ES are still tight at the seating depth with best accuracy, and if necessary, make tiny adjustments in charge weight to get tight SD/ES back

 

[Ryridesmotox]

I've never had a problem with wide SD/ES in my smaller groups. Mine are usually around 10SD and 21ES, or at least the last few chrono days. I have groups that are 1moa or larger that produce good SD as well, but from my understanding, the barrel is not in a calm state at that point. It's in the middle of the arch of movement. I've noticed that as I increase case volume, I reduce SD/ES numbers. Running slightly compressed loads has done well for those numbers for me. But that's an example of one person.

 

[918v]

How accurate is your scale? Cuz with most scales 45.4 and 45.6 overlap. The scales are that inaccurate.

 

[Ryridesmotox]

I use a Dillon Ohaus beam and make sure every charge is as accurate as possible. I'm pretty confident its within .1 grain. And I use a forester micrometer seater. So I'm fairly confident in consistent CBTO length. I also measure every cartridge to make sure CBTO is the same... Especially during load development.

 

[918v]

I’m pretty sure your scale is not within .1gr

Eliminator Balance Beam Scale (13480): Reloading: Powder Scales

Eliminator Balance Beam Scale (13480): Reloading: Powder Scales

www.dillonprecision.com

 

[Ryridesmotox]

I mean, it says .1gr +/- right there. I trickle in to the kernel, so its plenty accurate.

But the intention of the thread was to talk about how the barrel harmonics affect the grouping/load developement. I am trying to get some info about that. Not about equipment for reloading

 

[RegionRat]

When you found the powder charge you liked, did you test again on that same charge as well as the ones next to it? Sometimes, the statistics line up against us and random outcomes fool us into believing we have a node when we don’t.

A good node should be on the order of 0.3 grains or more wide. If it isn’t, the slightest shift in one of several variables can move you off of it. For example, brass condition, temperature changes, component batch variations, etc.

To shed some light on why a higher or lower node isn’t as important as the width of the node, imagine two identical test barrel rigs that shoot the same bullet though a similarly profiled bbl. Let’s just say for instance a 308 WIN versus a .30-06. Because there is some overlap in their velocities with an identical bullet, it makes for a good example to understand that the bbl may not care which velocity node we are on since those two examples may go to the same node, but the high one for a 308 might be a low one for a .30-06, and the same bullet launched faster in the 06 may go to a node too high for the 308. They are all good nodes if they are wide and forgiving.

Sometimes we get lucky and the velocity node, and the vibration nodes, line up in our favor. When that happens, we have an insensitive rig that shines at distance and accuracy.

So, check again before you commit and load in bulk, test in that range and check seating depth and case prep sensitivity too. Using tests with about 10 to 20 rounds helps with competition rigs since strings can be 20 rounds at a time plus sighters, and for field games, all that plus cold bore tests.

 

[918v]

I mean, it says .1gr +/- right there. I trickle in to the kernel, so its plenty accurate.

But the intention of the thread was to talk about how the barrel harmonics affect the grouping/load developement. I am trying to get some info about that. Not about equipment for reloading

You said that a difference of .2 grains of powder affects your barrel harmonics.

I said that your scale isn’t accurate enough to validate your observation because there is too much overlap.

A difference of .2 grains is not enough to affect barrel harmonics to the degree you claim.

 

[Yote Klr]

Repeat the same loads, see if the results are the same. My money is the results will not repeat itself. I wouldn't consider a load that is dependent on only .02gr.

 

[ken4570tc in WY]

I'm going to argue for searching for the widest node possible within a reasonable operating velocity range. The reason is that changing powder temps could kick you out of a narrow node. Also, less trouble adjusting charge to get back in a node after changing lot numbers for powder or primers.

 

[ditter]

Can’t answer your specific question on the harmonics, but a chronograph can/will solve the question node.

I find a charge weight with low SD/ES first, and during this stage I don’t worry about groups, I usually shoot at steel. After finding a charge weight with low SD/ES, I do a seating depth test. Tightest groups wins the development. Confirm the SD/ES are still tight at the seating depth with best accuracy, and if necessary, make tiny adjustments in charge weight to get tight SD/ES back

100% correct above. You cant really do a OCW test without a chronograph. You're not looking for an accuracy node. Youre looking for a velocity node. If you have no idea what your velocities are, you are relying solely on your groups. But your groups are subject to shooter error. Velocities are shooter error-proof. Dont even worry about groups. You could literally shoot into the berm.

I bought a Magnetospeed sporter and it's great. I got so much info out of it that I wish I had bought it months earlier. It would have saved me tons of time and ammo.

 

[Deleted member 113831]

To answer your specific question, higher nodes are generally finickier because of what your powder is doing at the top of the pressure curve. Pressures get spikey at the top. A load that works well today, may not work as well tomorrow...or from one season to the next.

Just how finicky it may be depends on too many factors to predict.

I'm a middle node guy, I'll even accept a load that is a little less accurate, if it will remain consistent throughout the year.

But until you start shooting larger groups (10 rounds or more) at distance (200+ yards), you don't really know what kind of load you have anyway.

 

[Precision Underground]

Don’t read into OCW groups so much. You should not be looking for small groups in an OCW test. You are looking for a node that prints vertically consistent over the widest spread of charges as possible. You are likely reading shooter error, not differences in charges.

 

[supercorndogs]

100% correct above. You cant really do a OCW test without a chronograph. You're not looking for an accuracy node. Youre looking for a velocity node. If you have no idea what your velocities are, you are relying solely on your groups. But your groups are subject to shooter error. Velocities are shooter error-proof. Dont even worry about groups. You could literally shoot into the berm.

I bought a Magnetospeed sporter and it's great. I got so much info out of it that I wish I had bought it months earlier. It would have saved me tons of time and ammo.

You do not need a chronograph to do an OCW. You absolutely can not do an OCW test with out a target. OCW is determined by POI, not SD not smallest group, not vertical spread. You can't read it with your chromo, you can't shoot into the berm.

Everything about OCW is free to read online. I am stunned so many talk about it with authority, and clearly have not read one iota of the material available.

 

[Precision Underground]

You do not need a chronograph to do an OCW. You absolutely can not do an OCW test with out a target. OCW is determined by POI, not SD not smallest group, not vertical spread. You can't read it with your chromo, you can't shoot into the berm.

Everything about OCW is free to read online. I am stunned so many talk about it with authority, and clearly have not read one iota of the material available.

This.

 

[Ryridesmotox]

To answer your specific question, higher nodes are generally finickier because of what your powder is doing at the top of the pressure curve. Pressures get spikey at the top. A load that works well today, may not work as well tomorrow...or from one season to the next.

Just how finicky it may be depends on too many factors to predict.

I'm a middle node guy, I'll even accept a load that is a little less accurate, if it will remain consistent throughout the year.

But until you start shooting larger groups (10 rounds or more) at distance (200+ yards), you don't really know what kind of load you have anyway.

Ah yea that's more the answer I was going for, with the pressure etc.

Don’t read into OCW groups so much. You should not be looking for small groups in an OCW test. You are looking for a node that prints vertically consistent over the widest spread of charges as possible. You are likely reading shooter error, not differences in charges.

Yea the 45.2-45.8gr printed all about .5 above that horizontal line center to center. It's an acceptable node that I need to look at further. But I think I'm going to back down to a lower node to get better brass life.

I'm going to play with seating depth and neck tension a bit. It's a 308 so throwing a few k rounds down range to figure out good processes doesnt bother me. If it was 6xc or some such, I'd want to find a load in about 20 shots to roll with

 

[Ryridesmotox]

You said that a difference of .2 grains of powder affects your barrel harmonics.

I said that your scale isn’t accurate enough to validate your observation because there is too much overlap.

A difference of .2 grains is not enough to affect barrel harmonics to the degree you claim.

Missing the point of the thread. It's not about reloading process. It's about how things beyond one's control effect reloading nodes. Like harmonics or, like above, how powder reacts to pressure.

 

[Ryridesmotox]

I’m not missing the point. I’m pointing out to you that your conclusion about accuracy nodes is wrong.

That the accuracy nodes in higher charge weights are narrower? I'm not saying my method of testing is sufficiently accurate for this type of testing. I honestly wouldn't even know how to test this sufficiently. It's just observational. A lower node in my rife is twice as wide as the high compressed powder load node that I was testing. I wasn't drawing any conclusions as yet, it's all just kind of abstract thought. Just trying to see what people were thinking here that have more experience.

With my rifle, I can load a 41.0-42.8gr load without much vertical POI shift. With the current load, I'm between 45.4-45.8gr, before and after that range is a pretty decent verticle POI shift... Regardless of the size of group, measuring center to center. Size being less important to the testing, I didnt take pictures of my other parts of the OCW test, or I can't find them on my phone for some reason.

 

[sixtyfournmor]

I don't think it was the difference in your load. More like the difference in your shooting.
Get it close to where you want it and shoot a bunch, you'll see that much difference on any different day.

I never go max or even near max loads any more. Find a load close to max and back down from that.
It'll shoot just as good over a given time as a full throttle load. The last 100fps don't mean anything.

A consistent load means everything. Cold weather, hot weather, cold barrel hot barrel, how you hold the rifle etc.
Tight cheek weld, weak cheek weld, tight to the shoulder loose to shoulder, left hand out front, or in close.
Worry less shoot more. These things all by themselves could do what happened to you.

 

[jsthntn247]

Shoot a ladder test if you want to see effects of barrel harmonics. When shooting an OCW, the reason the poi changes between groups or doesn’t is because of barrel harmonics also.

 

[padom]

Yawn. This has been beaten to death.

Your group size should ALWAYS be ignored during OCW. Find that consistent POI then go do a seating depth test to shrink your group size. I ALWAYS find a seating depth that shrinks up and stands out from the rest. Except for 6BR, they are all tiny. Haha