Ladder Test: FPS between Accuracy nodes?

[pastorcurtis]

My Enfield in 303 Brit responded great to a ladder test with a 311041 clone (powder coated and gas checked) with H4895 powder. I've found one accuracy node around 1750 fps.

Is there a "typical" velocity differential between accuracy nodes? Or at least a minimum velocity differential?

In 308 Win I've got the same boolit running at 2000 fps. It would be nice to know there might be another accuracy node north of 1750 for the 303 Brit. But if the next one is not likely to exist until, say, 2300+ then I'd know not to bother as I don't want to run it much north of 2000.

Thanks!
Pastor Curtis

[Hick]

Someone with more expertise will, hopefully, also respond, but I've done many ladder tests for accuracy with my Enfield, Mauser, M1 and several other rifles. I don't see any consistent step of velocity between the nodes. There is a great article on the internet with one of the theories about why there are accuracy nodes (sorry-- I read it but didn't keep the link). The theory was that the nodes are caused by the way the expansion of the chamber travels up and down the barrel (like ringing a bell). If this theory is right, I would think that the steps between nodes would depend mostly on the length and properties of the barrel (wall thickness, type of steel, etc), and the size and speed of the first pressure pulse. Its interesting, but I don't know how to translate this into a prediction.

[OS OK]

Good question, don't know if I can give an answer other than to show you what I have experienced using a Rem 700 Varmint Bull Barrel .308W & 168gr. Sierra BTHP's powered by Varget and CCI LRP's.
You can see for yourself the speed differences between load increments and I think I see two potential nodes here that either might be improved by OAL and nearness to the lands adjustments alone.
All shots I called good in that I did not call any fliers in these 5 shot groups.

Open grouping...

https://i.imgur.com/pIgo943.jpg?1

Between this potential node and the next is 73fps.

https://i.imgur.com/Dimxsfs.jpg?1

Open grouping...

https://i.imgur.com/L4BXlDS.jpg?1

2'nd potential node.

https://i.imgur.com/m5ZkF1J.jpg?1

[charlie b]

If a barrel is free floated a program like Quickload can estimate the nodes for you.

When something else comes in contact with the barrel all bets are off as you have too many other things damping the barrel vibrations.