rockhound78
Silver $$ Contributor
Is there a list of the speeds where nodes exist or does it vary by caliber?
Thanks
Thanks
velocity nodes?
- Thread starter rockhound78
- Start date
Every single barrel is different. Some are close but unique
whatwind?
Silver $$ Contributor
listed by milliseconds from Quickload data and this, there are more “nodes” but in my limited experience these do get you started
http://www.the-long-family.com/OBT_paper.htm
Here is a calculator:
https://pierrevanderwalt.com/obt-calculator/
As others have mentioned, it is different from barrel to barrel - not only length. The barrel profile also plays a role, ie, a bull barrel of the same length will have different node values. The calculators typically just act as a guide, and not all nodes are actually possible to reach with a specific calibre (note the complete absence of the mention of any calibre with any of these calculators) , so don't blindly chase a value you get back from a calculator. You typically use this along with something like Quickload to also make sure you have a powder that gives you best case fill and stays within safe projected pressures.
In general, you add more powder, or seat deeper (or both) to get to a node with smaller ms value.
So you would start by getting a range of node values for your barrel length, then you start playing in QL to see what powder charge (or seating depth etc) is going to get you to the muzzle velocity that equates to the barrel time value in milliseconds. You stay within the "safe" pressures, choose a load, then go shoot it and verify speed. If it's slightly off, you go back in QL and start adjusting powder burn rates etc, untill QL and your chrony matches as close as possible. After that, you are "calibrated" and can start playing with charge properties in QL to see how (if) you can get to other nodes safely. As you go through this exercise, you will also quickly see if your barrel is exactly on the predicted nodes from the calculator, or whether they lead/lag by a little (you verify this on paper - tighter groups will generally be closer to the node).
https://pierrevanderwalt.com/obt-calculator/
As others have mentioned, it is different from barrel to barrel - not only length. The barrel profile also plays a role, ie, a bull barrel of the same length will have different node values. The calculators typically just act as a guide, and not all nodes are actually possible to reach with a specific calibre (note the complete absence of the mention of any calibre with any of these calculators) , so don't blindly chase a value you get back from a calculator. You typically use this along with something like Quickload to also make sure you have a powder that gives you best case fill and stays within safe projected pressures.
In general, you add more powder, or seat deeper (or both) to get to a node with smaller ms value.
So you would start by getting a range of node values for your barrel length, then you start playing in QL to see what powder charge (or seating depth etc) is going to get you to the muzzle velocity that equates to the barrel time value in milliseconds. You stay within the "safe" pressures, choose a load, then go shoot it and verify speed. If it's slightly off, you go back in QL and start adjusting powder burn rates etc, untill QL and your chrony matches as close as possible. After that, you are "calibrated" and can start playing with charge properties in QL to see how (if) you can get to other nodes safely. As you go through this exercise, you will also quickly see if your barrel is exactly on the predicted nodes from the calculator, or whether they lead/lag by a little (you verify this on paper - tighter groups will generally be closer to the node).
Last edited:
rockhound78
Silver $$ Contributor
Thanks for the info
tag
I tend to differ, in simple terms, if you have a rod (rifle bbl in this case) and 'ring' it (tap with hammer at the fixed end), the vibration pattern is linear through its length and this energy will pass from source to the open/free end and back to the source (receiver) . As this annular ring (energy ring) passes from fixed to free end and back, it will affect the bullets rate of acceleration. so absolute velocity at the muzzle will vary with different bullets. Suffice to say the muzzle must be the calmest and tightest when the bullet is released.
In carbon and stainless steel it is ~18-19 000 ft/s, I think stainless is close to 18 800 ft/s, this gives , at a bullet velocity of 3 000 ft/s, gives 6 opportunities for the muzzle to be calm, two are generally useful.
The barrel does not whip up and down however it does show displacement as the energy pulse travels from fixed end to free end.
I have been loading ammo through QL to obtain a barrel time (mS) and and OCW. Most any mechanically sound rifle /scope combo will produce sub moa groups.
Last club shoot at 540 yards/ 10 rounds netted sub moa groups with the 4 rifles I brought. These are not dedicated bench rifles, but rebarreled Tikka's in 6 Dasher, 260 Rem, Savage 6 Dasher, and a stock Tikka/Tactical in 300 WM. If I could read the wind better groups would have been smaller, but good enough for two podiums in challenging conditions.
All were load the same way and charge weights were decided by the use of QL and the OBT and OCW theories.
In carbon and stainless steel it is ~18-19 000 ft/s, I think stainless is close to 18 800 ft/s, this gives , at a bullet velocity of 3 000 ft/s, gives 6 opportunities for the muzzle to be calm, two are generally useful.
The barrel does not whip up and down however it does show displacement as the energy pulse travels from fixed end to free end.
I have been loading ammo through QL to obtain a barrel time (mS) and and OCW. Most any mechanically sound rifle /scope combo will produce sub moa groups.
Last club shoot at 540 yards/ 10 rounds netted sub moa groups with the 4 rifles I brought. These are not dedicated bench rifles, but rebarreled Tikka's in 6 Dasher, 260 Rem, Savage 6 Dasher, and a stock Tikka/Tactical in 300 WM. If I could read the wind better groups would have been smaller, but good enough for two podiums in challenging conditions.
All were load the same way and charge weights were decided by the use of QL and the OBT and OCW theories.
Sandstorm
Gold $$ Contributor
Speed to me is irrelevant if your seating depth is not optimized.
Once you have that equation in order you can push the speeds....at least in my endeavors ive found this to be true.
By all means...whatever your obsessions..These are just my OCD endeavors at work, and everyone will find their own
conclusions by their own preferred methods.
Once you have that equation in order you can push the speeds....at least in my endeavors ive found this to be true.
By all means...whatever your obsessions..These are just my OCD endeavors at work, and everyone will find their own
conclusions by their own preferred methods.
How does a tuner change the OBT?
OBT is the practice of tuning ammo so that the bullet exits the muzzle when the muzzle is not moving or moving the least. By placing a weight on the end of the barrel, whether it is in the form of a brake, suppressor or Tuner, the harmonics of the barrel are changed. By moving the weight slightly, the vibration pattern of the barrel can be modified to account for temperature and atmospheric changes from day to day that tend to speed up or slow down the bullet as it travels down the barrel which otherwise may allow it to exit the muzzle at a less than optimal time.
In practice we tune the load to exit the barrel at OBT, then use the tuner to keep it tuned without the need to vary charges during the day as the temperature changes, or day to day to maintain OBT and tightest groups.
Loading at the bench to keep the rifle shooting its best is a valuable skill developed through years of practice and a good amount of patience and understanding. Some will opine that's what separates the average shooter from a top notch shooter, and they'd be right. But it's not a skill just anyone can develop. The tuner is a shortcut method of accomplishing the same thing.
A tuner will help keep a well developed load shooting at it's best. What it won't do is make a poor load shoot well consistently.
In practice we tune the load to exit the barrel at OBT, then use the tuner to keep it tuned without the need to vary charges during the day as the temperature changes, or day to day to maintain OBT and tightest groups.
Loading at the bench to keep the rifle shooting its best is a valuable skill developed through years of practice and a good amount of patience and understanding. Some will opine that's what separates the average shooter from a top notch shooter, and they'd be right. But it's not a skill just anyone can develop. The tuner is a shortcut method of accomplishing the same thing.
A tuner will help keep a well developed load shooting at it's best. What it won't do is make a poor load shoot well consistently.
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