"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