"drinks" on the Cast Boolits forum referred me to (You need to Login or Register to view media files and links) and Christopher Long's "Acoustic Shock Waves and the Optimal Barrel Time loading concept!"
I printed the 17 page paper and have read it maybe a dozen times. While I'm still unclear on some of it, this paper presents a predictive model for a set of accuracy zones determined by the optimum barrel times.
If we select one of the array of optmum barrel times corresponding to a node, then fiddle with Quickload to select a load with that barrel time, then that load (or one very close) should be a local accuracy maximum.
Christopher Long's model was derived, if I understand the paper, using relatively high speed jacketed bullets and close-to-full cases of powder.
In all I have read about barrel vibrations and harmonics and nodes (much, I suspect, due to that picture of the vibrating barrel in the Lyman handbook), this is the first predictive model I can remember. 
Now, does it work for cast bullets?
To find out, we can approach this thing from the other end. If we list a lot of accurate loads and their associated information, then we can plug that information into Quickload and find the barrel time for each load. We can then compare that barrel time with the array of optimum barrel time nodes, and see if the two barrel times match or are related.
So, will some of you send me your most accurate loads and info?   
Here's what I think is needed:

Barrel length (inches, bolt/breech block to muzzle)
Cartridge (Ex: 308 Win.)
Bullet  (Ex: Lyman 311041)
Bullet weight  (grains)
Bullet length  (inches)
Powder  (Ex: Unique)
Charge  (grains)
OAL  (cartridge overall length, inches)

Please send them here or to joeb33050@yahoo.com

Then I'll find some folks with Quickload to figure the barrel time, and compare the numbers to the numbers on the spreadsheet that I made. (I'll be happy to send the EXCEL spreadsheet to anyone who wants it.)

Maybe this will give us a method of predicting and finding accurate loads much faster and less expensively.

Thanks;
joe brennan 

Joe

It's a theory I don't believe

Boats

boats wrote on Jun 12^th, 2007 at 11:58am:

I read it and the associated links stuff. There seems to be some/a lot of support in the jacketed bullet world. 
It seems to be worth testing.
It's (for me) very hard to read and understand. 
What makes it hard to believe?
By the way, the picture is PP 98 and 99 of Lyman's 47th. 
joe brennan

This seems similar to the theory supporting the ladder method for developing loads  -FWIW, IME that one does seem to work...  The originator was some german scientist some time before WWI.  An article on it here:
(You need to Login or Register to view media files and links)

For your reading pleasure, enjoy. [url]  (You need to Login or Register to view media files and links) [/url] 

boats wrote on Jun 12^th, 2007 at 3:56pm:

While I don't doubt that they flex - I don't see how prone or sling shooting can prove anything about the fact that they flex.

Quote:

Maybe - maybe not.  I will say that I consistently need 2-4 MOA of elevation if I move the front rest from the forearm to just back of the muzzle.  Flex seems to be a good explanation (as opposed to vibration).   

I'm reminded of the test Old Harold McFarland wrote about many years ago to show how vibration effected a barrel.

He placed a barreled action in a vise and laid lead wires across the barrel in four equal divided places. He then wacked the receiver in the vise with a leather mallet. 

The effect was interesting to note how the wires moved into different positions.

As I recall, this is what he referred to (the position of the wires) as the nodes.

I don't pretend to know the answers to questions about barrel harmonics, but I do know the answers I've gotten when I've asked every top flight barrel maker in the country, about what taper and length gives the best accuracy. To a man the reply has been, minimum taper, thicker dia and shorter length.

Quote:



It is interesting to note that Bill Calfee does not agree with this with respect to .22 barrels and he is definitely a person to be respected in the .22 benchrest world.  Thin barrels plus tuners win out as far as he is concerned.

Brent