Looking for Velocity Node data for .223

[mjgillen]

Hello All,

Fairly new to accurate shooting but trying to do my research. Not knowing what a "node" was I did a search and stumbled upon some info on Velocity Nodes that I thought cleared some things up for me. As I understand it, when working up an accurate load, there is a sweet spot ("node") where the bullet leaves the barrel consistently providing the stability to shoot accurately. Of course the shooter has to do his/her part as well.

One article says the nodes are consistently 120fps apart and that as you work up loads (ladder?) your groups will get tighter as you approach and hit the node velocity then open up again as you go past the node velocity range. Very interesting that the nodes are all about velocity. Here is a quote from the post about 6mm "Honey Nodes/Velocities":

These velocities are typical for your 105-108 bullets. So the "honey nodes" appear to be at

2720-2750
2820-2850
2920-2950
3020-3050

1. These "honey" numbers don't care what the rifle is or even what the cartidge is (assuming the barrel is a LV, HV or straight "typcially quality benchrest rifle" with a barrel of 24-30 inches)....

So my big question is: Do these velocity node numbers also hold true for the .223 Rem? Is it really as simple as hitting a velocity? I am interested in working up an accurate load for my Savage 12FV 1:9 twist 26" bbl .223 Rem 73gr Berger pills and need all the help and advice I can get. And if these nodes really are true, I'm excited to understand them and find my own sweet spots.

The post I mentioned is here: http://forum.accurateshooter.com/th...in-typical-bench-gun-barrels-for-6mm.3784402/

Thanks in advance,
Michael

 

[CharlieNC]

Read some more. Google Optimal Charge Weight (OCW) by Dan Newberry and Optimum Barrel Time (OBT) by Chris Long for more insight.

 

[Ned Ludd]

"Accuracy nodes" are dependent on pressure and velocity, which are dependent on barrel length, powder/specific lot, primers/specific lot, bullet/specific lot, case volume/specific lot, ambient temperature...the list goes on. Trying to guess at a certain velocity MIGHT get you in the neighborhood, but only if you have reliable velocity data for an accuracy node in a rifle/load that matches your specific setup (i.e. powder, bullet, primer, case, barrel length, etc.). Even then, you will need to do load development, test, and determine empirically which combination shoots the best.

If you really want to try and predict as much as you can up front, thereby limiting the amount of reloading/testing you need to do, I would suggest taking a look at Chris Long's website for Optimal Barrel Time Nodes and his instructions on how to use Quickload (reloader's computer program) in combination with his theory (link below). Quickload is a program that allows you to input your rifle/load specifics (bullet, barrel length, COAL, case trim length, case volume, charge weight, etc.), then manipulate the values to get predictions on what the different changes will do to pressure and velocity. I find it very useful.

In the case of Optimal Barrel Times Nodes, Chris Long has generated a table of barrel time values, which is one of the Quickload outputs, for various barrel lengths. For that reason, you can use Quickload to target a specific barrel time (or narrow range) by adjusting charge weight to change pressure/velocity. The caveat is that the factory preset values for burn rates of all the different powders available in the pull-down menu will likely not match your specific caliber/bullet and/or lot of powder and primer combination. So you need to load up a few rounds at a known charge weight, determine the actual average velocity, then go back into the program and adjust the preset powder burn rate until predicted velocity exactly matches measured velocity. Once you have "calibrated" the program to your specific setup and components, the predictions are usually very good.

If you use conventional testing methods such as ladder testing, OCW, etc., you MIGHT be able to find velocity data for a setup that is pretty close to yours. However, all the other variables mean that at best you may identify a certain velocity range that you then need to test to see where your specific setup shoots best. Frankly, there is more than enough dat out there that it is easier to just load up a charge weight test series and go shoot them of a fairly wide velocity range, and determine directly where you need to be. Once you have identified the charge weight window, you can then optimize seating depth in the same way.

Quickload is no free lunch, it simply allows you to target a specific barrel time from a Table of predetermined values for various barrel lengths, rather than by covering a much wider range of pressure/velocity to empirically find the "sweet spot". In my hands, the use of Quickload and OBT Nodes has worked very well, but you still have to do a certain amount of development and testing to find the best combination. It just allows you to narrow the range over which you test, thereby providing some savings on time and components.

http://the-long-family.com/optimal barrel time.htm

http://www.neconos.com/details3.htm

 

[linedrive301ft]

gstaylorg, well said. This works for me.