Barrel Nodes

[chrisward3]

Looking for input on finding barrel nodes.

Are they based on Velocity, Barrel Pressure, both?

The reason I ask is, if I found a good node with LOAD "X" and switch powder, lot, etc... could I achieve the same results if LOAD "Y" had a matching MV or pressure?

 

[Cwoods]

That's a good question! Will definitely be watching this thread. I am relatively new to reloading reloading. I have stuck with my best loads exclusively.

 

[excaliber]

This question should be asked on 6BR.com. Your getting ready to get a dozen different answers. Changing anything (lots) will change the velocity, pressure,
which will change the accuracy node.

 

[Lukas Koukal]

The closest the "nodes" are linked to is a function of muzzle velocity and pressure, that is if you´re referring to the OBT concept. The notes consider the time it takes for the bullet from the ignition to leave the bore. MV alone is not enough, since different loads speed up to the same resulting MV differently. Quickload gives you the time of the bullet travel in thousandths of milliseconds, that´s what I´m using.

 

[Rthur]

A node is , as I understand it, a part of the vibration cycle where your barrel is in a good position upon bullet release. So to speak the bullet is exiting while the barrel is calm in the vibration cycle. I have read that there are 5 cycles that happen in the barrel before the bullet can exit. I cannot verify this as I don't have the equipment to do these tests. All of the science doesn't really matter as doing a ladder test with your rifle with your load should give you the answers you are looking for.

r

 

[VKC]

Looking for input on finding barrel nodes.

Are they based on Velocity, Barrel Pressure, both?

The reason I ask is, if I found a good node with LOAD "X" and switch powder, lot, etc... could I achieve the same results if LOAD "Y" had a matching MV or pressure?

In theory yes, in practice not necessarily. Another factor to consider is variations in fill ratio with different powders and how that effects consistency.

 

[diderr]

A lot of things will vary in finding nodes. Barrel length, thickness, type of steel. Every barrel will be different and every component will be different. Nodes also relate to OCW more than anything. The best way to find accuracy nodes is ladder load development at 300 yards or further.

 

[OneShotJim]

For good info on Optimal Charge Weight (OCW) approach to load development see:

OCW Overview - Dan Newberry's OCW Load Development System

Some enlightening reading on Optimal Barrel Time internal ballistics can be found at:

Optimal Barrel Time Paper

Note that since there are lots of variables involved, my experience has been that the OCW method is a workable practical approach to finding good accuracy nodes for a particular rifle/barrel, even if you only have a short range (100-300yd) to test on. I'm not one to argue over OCW vs. ladder tests. Ladder tests can work fine too, especially if you have a longe range to test on.

Donovan Moran, in a thread on Practical Riflery Forums, outlines his method, which in my opinion combines the best features of both OCW and ladder tests, see. (Of course, not everyone can set up their test like he does.)

OCW <> 5-hours <> ½-MOA in Technical stuff... Forum

To me the bottom line on all this is that barrel time can be calculated, but practically, one has to test at a range of loads to see how a particular rifle/barrel actually performs. Also, all the above isn't nearly as hard as it sounds. Be sure to keep asking questions as you proceed. There's a wealth of knowledge on the Hide!

 

[chrisward3]

thanks for all the replies guys!

 

[RUMrunner]

I asked this same question of an experienced hand loader and he told me in a long roundabout way a less than definitive no. As in maybe it can be done, but I can't do it. I guess I just have to put in my time for load development.