load to the node?

So I was on Fb and a fellow on a reloading page asked a question and it went crazy with a lot of opinions. I did not voice mine. I am going to try and ask you fellows what you think.

His question was ,"do most loads usually hit its accuracy mark at around the same velocity or node".

A lot of guys were saying no. Now, I have seen on this site many times that folks will say they hit say, a 6 bra at 2950-70. Or, a Dasher at 3050. I honestly cant recall all the numbers but, it sort of holds true to see where accuracy hits at a certain velocity. No matter which powder that is used, a certain velocity tends to be the most accurate. If you use varget, h4895, or whatever, you tend to find the accuracy at a almost set velocity.

Now it goes without saying there is fine tuning in any situation. I"m just talking about pure velocity vs accuracy.

What you guys think?

 

I never really thought about it in those terms. I can say that some people with the same barrel length report good nodes that are close to the velocities where I mine are, but I would tend to think it is either more of a coincidence or just people jumping on to be part of the conversation if it happened all the time. Different barrel lengths, different stress relieving (resulting from contours, different groove count, other), and even different bullets, seem like they would prohibit that from being universal.

But I am just thinking out loud. I really don't know.

 

Not necessarily. Loads with the exact same bullet weight, powder, and barrel length, can often have "accuracy nodes" that fall into a relatively narrow velocity range, but it's not written in stone. For example, I have loaded 185 gr bullets in .308 Win rifles with 30" barrels using Varget and H4895 for years. In my hands, loads with 185s almost always tuned in at approximately 2720-2730 fps with Varget, and approximately 2740-2750 fps with H4895. However, lengthening or shortening the rifle freebore, and hence the seating depth and effective case volume, can have noticeable effect on the velocity of tuned loads, sometimes shifting the velocity of an "accuracy node" by as much as 20-30 fps in one direction or the other. Even rifles that are seemingly almost identical don't always tune in at the exact same velocity. In that context, differences of +/- 20 fps are almost routine. So claiming that accuracy nodes are always linked to very specific velocities is a dubious claim at best.

I would say in the grand scheme of reloading it's probably safest to make a fairly general statement that you are likely to find accuracy nodes within a certain velocity range with a given caliber, powder, case volume, barrel length, bullet weight, etc. In other words, the more specific the claim is made, the more likely there will be outliers that cast doubt on the validity of the claim.

 

I dont disagree one bit. But, I find it funny that a lot of calibers from what you read on here, are on their node within say 25-50 feet of each other.

 

Cant say I disagree. I can be influenced. HA. Everything that you have said is very true also. And, maybe the forum pages I have read, they tend to be pretty much alike. For instance if someone asks about a 6 dasher load and these guys are all shooting relatively the same barrel length, of course caliber, they are br guys and follow generally a same path it is only logical that the velocities are going to be close to each other.

Then again, maybe Im over thinking it.

 

Barrel time correlates closely with velocity, but not perfectly, so it can get you in the ballpark. But to find the exact node where the barrel time syncronizes with barrel harmonics requires testing.

 

I consider accurate velocities as fairly reliable in coincidence, as all other components fairly well matching.

 

I think it’s all about barrel time rather then velocities. So thinking that way if you are using powders with similar burn rates . It would look like velocity is what matters but really what’s happening is the bullet is in the barrel for the same time do to the burn rate .

Maybe if you comepared a fast for cartridge powder to a slow for cartridge powder producing the same velocity . You may not be in that same node because they would produce different barrel/dwell times ???

I don’t know just thinking out loud here , what say you ?

 

I definitely do not think a 20 inch sporter in 308 should have the same node as a 31 inch palma rifle. This is as you say due to burn rate and dwell time. Not to mention the whipping of a lightweight sporter barrel. But, I do find interesting that fellows that shoot the same relative type rifles/calibers all do find their node/velocity to be VERY close. THey may have to mess with seating depth, neck tension or whatever to achieve ultimate accuracy, the velocity is still close. It isnt going to be exact but it is still dang close.

 

I somewhat agree that velocity and accuracy nodes seem to have some correlation. An example of this is the 30BR crowd. They all seem to be huddled around one powder, within a few tenths of a grain, one bullet within a few grains, and a very similar velocity. This is an example of individually tuned rifles.
Then you have the 6.5 CM factory ammo as an example where you cannot adjust the ammo, but for a lot of them, they get very accuracy. The factory ammo can only somewhat control things like case fill, powder selection, velocity and pressure in a test barrel, and a few other things. Yet it seems that they produce accuracy good enough for a wide variety of rifles with totally different configurations.
It is just a matter of how accurate is accurate to you.

 

I thought the guys here were looking for the node at the fastest speed to get best tajectory. Since I don't shoot over 500, I look for a slower node to get barrel life and less recoil, etc. Never considered the fastest node might be the most accurate???????

 

I do not load to the highest node. I prefer to load to the lower nodes to reduce recoil and also to avoid potential pressure hazards. I shoot PRS matches. Sometimes it is very hot and sometimes we may be shooting in the rain. I would not want to be loaded at max pressure and put a wet cartridge into the chamber.

 

That one (fastest is the most accurate) I will say based on personal experience, it is highly suspect. I mainly shoot 26" barrels and regularly find 3 good nodes. I rarely try to find a next upper pressure spectrum load. I am not prepared to say that any one of them is more or less accurate as they for the most part are the same. I think what some shooters find is a narrow node, or catch the end of a node, so errors in loading show up and compound their personal shooting errors. This alone may translate to someone saying node A is better than node B.

I will say that for some caliber/rifle combinations that I have and have had, there has been one node that just 'felt better' so I shot that node better. Total head thing in my case.

 

My answer to your original question is yes! I see it time and time again with 6ppc, 6BRA and 6BR.

Bart

 

Count me in the “OBT Disbeliever” side. It’s all about harmonics.

 

Remember that all free floating barrels for a given cartridge with the same steel, weight, length and profile will have the same resonant vibration low frequency and several harmonic vibrations higher frequencies.

The amount and vertical direction the barrel bore axis vibration at the muzzle whips and wiggles at is determined by the load and bore/recoil axis above the rifle's center of mass and how the rifle's held.

Best accuracy happens when all bullets leave on the muzzle axis up swing so faster ones with less barrel times leave at slightly lower angles to the LOS than slower ones with more barrel times that'll leave at higher angles.

Therefore, the same load will shoot equally accuracy across several rifles with the same build specs. This was common with military teams shooting the same spec'd rifles

 

Say we're load testing at 100 yards and the bullets are leaving on the muzzle axis upswing, do the faster bullets print lower on the target compared to the slower ones ?

 

Yes. If the load causes the bullet's trajectories cross at about 200 yards.

If you use ballistic software plotting 2 trajectories to zero at 200 yards with a 25 fps muzzle velocity spread, note the trajectory height above LOS at 100 yards for each velocity.

Some people put tuning weights on barrels near the muzzle then move them tuning the muzzle axis vibration frequency so bullets leave at the right LOF angles on the upswing.

This site explains how it works:

https://www.varmintal.com/aeste.htm

 

There is a reason we strive to have each cartridge loaded with the exact same brass, primer, bullet and powder. Many will separate each component according to weight and measure their powder to the tiniest degree possible. In an ideal world, doing this will give you the same velocity. It stands to reason, that if your velocity varies, point of impact will vary. Think slo pitch softball as opposed to a 95 MPH fastball.

 

I think I understand what you are trying to say, but it is an oversimplification. Two paths (fast, high BC, low angle - aka fast ball vs. not so fast, okay BC, high angle - aka slow pitch) can hit the same point of impact. The consistency with which each of those paths can be repeated is what I believe you were talking about.