Most of you who click on this thread will have already read the debate regarding my OCW load development method versus the traditional Audette "ladder" method.

I wanted to seperate the issue from the thread where that debate was flourishing, as this is a distinctly different issue.

I've given several reasons for why I believe the OCW load development process is easier to execute, and also why I believe the information is more useful than the information obtained from the Audette method. So I won't rehash those reasons here, unless asked.

What I wanted to point out in this thread is the quality difference in an OCW load versus a load arrived at via the Audette method.

Click here for a sketch of the muzzle's harmonic whip cycle, and a brief explanation of the effects of this cycle on rifle accuracy: http://home.earthlink.net/~dannewberry/_wsn/page2.html The harmonic whip sketch is half way down the page.

With the conventional Audette method, the propensity exists for a good harmonic node of the barrel to place four or five shots close together even though their velocities are hodge-podge. That's the nice thing about a good harmonic node, but it's the fly in the ointment in the Audette test.

Here's why: Just as a good harmonic node can place several shots that don't belong together in a nice little group on the target, the opposite is also true. If the muzzle is going through a "straightaway" of the harmonic whip cycle just as the most consistent velocities are being encountered, these shots will "string" on the target.

Example: You're shooting the 165 grain bullet in a 30-06, with IMR 4350 powder behind it. You begin the 20 shot Audette method at, say, 54 grains, and intend to work your way up to around 59 grains. You note that there is a tight group of five shots ranging from 55.2 to 56.1 grains. You're hopeful that a charge of about 55.7 grains would get you consistent, nice groups at 300 yards with this rifle. And in truth, you'd be right...
However, as the charge weights increase, you move through the 57.5 grain charge weight range while the barrel is "whipping" through a straightaway of the whip cycle. Here, the velocities are tighter than anywhere else above or below that charge, but you won't know it by the target at 300 yards, because the three shots that would have shown you this (57.2, 57.5, and 57.8) strung diagonally on the target. The Audette method will have steered you toward a non-optimized charge weight which will need a good harmonic node to perform well.

It would be much better to locate the powder charge weight zone which offered the most consistent ignition and burn (hence the most even velocity), and then tune that load to coincide with a good harmonic whip node of the barrel.

Here you will have the best of both worlds, so to speak. You'll have a truly optimized powder charge and a node tuned load.

And that's the biggest reason why my way is better!

Dan Newberry
green 788

Jerry, that's an excellent question...

An Oehler 35 might be accurate enough--I'm not sure because I haven't used one for this purpose. I don't know what the error factor is on the Oehler, but you can take that number and decide for yourself if it would work.

In my opinion, it is much easier to simply shoot the "round robin" groups, triagulate, and decide which 9 shots came the closest to exiting the muzzle at the same point on the target, which should be a steady indicator of true average velocity--at least so at 100 yards. The triangulated groups should act to somewhat "average out" the effects of the muzzle's harmonic whip cycle, allowing you to better pinpoint the zone where the best 9 shots leave the muzzle.
Due to the effects of the harmonic whip cycle, the groups can look deceivingly awful, or deceivingly great. But pay no attention to group size at this point--these groups are of course being affected by the harmonic whip cycle. Group size can be tuned with seating depth variations after you've chosen the best powder charge.

Finding three consecutive groups which hit the target in the same general spot is the key. Then by choosing the powder charge from the center group, and fine tuning the load with seating depth adjustments to get to a good node, you'll have it...

I've updated page 4 of my website, and you may be interested in checking it out: http://home.earthlink.net/~dannewberry/_wsn/page4.html

Thanks for the thoughtful question. It appears that you understand the concept well...

Dan

[ 02-11-2003, 08:01: Message edited by: green 788 ]

Jerry--one other thing: You say "While I have loaded and shot some, I have little experience with an accurate rifle (ie. I have more rugers than remingtons, and no customs or replaced barrels)."

Many factory barrels are stunningly accurate. The Rugers built in the last four to six years have some pretty decent barrels indeed.

Unless there is something terribly amiss, you can get 3/4 MOA out of practically any decent factory rifle, and 1/2 MOA out of most of them. I honestly believe that, and such has been my experience.

Dan