Hey, Dan.

There's an article in the January 2003 Varmint Hunter magazine that reminds me somewhat of your OCW methodology, but the guy takes some completely different tacks.

The author, Bob Krzyston, argues for keeping precise load development records and letting the rifle "tell you" what it likes via the data. In that respect, his method is similar to OCW.

Where Krzyston's method differs greatly is that he first varies the seating depth for a given bullet and charge, looking for a sweet spot. Then he uses that sweet spot and varies the powder charge, looking for a sweet spot there. Both sweet spots, by the way, are based strictly on group size, not on where the groups fall relative to one another, as in OCW.

I'm wondering whether you read the article and what your reaction is. Using his method, Krzyston worked up a load for his factory Rem 700 .243 that he says shoots "consistently in the 3s, 4s and 5s, with an occasional group in the 2s."

Quote: Where Krzyston's method differs greatly is that he first varies the seating depth for a given bullet and charge, looking for a sweet spot. Then he uses that sweet spot and varies the powder charge, looking for a sweet spot there. end quote

I don't think that is the correct approach. You can get just about any "distance to the lands" to work with the right powder charge. Conversely you can make just about any reasonable powder charge perform with seating depth adjustments, which is what he's doing. These variables are not independent of each other.

What the author is doing is the same as saying "first I pour my cup of coffee and then vary the amount of sugar until I find the "sweet spot." Then I add a little coffee, or take some away until I find the other "sweet spot."

The thing that (in my opinion) many folks have to understand is that there is not a "distance to lands" sweet spot which is independent of powder charge. If there was, all we'd have to do would be to find that "magic" distance to lands, and we could forget about worrying with powder charges. Where the author of the article you mention errs (again, in my opinion) is he assumes that the bullet is going to "like" that certain distance to the lands regardless of the powder charge. There is no science which I'm aware of that would substantiate such a supposition. Look here for my reasoning behind this belief: http://home.earthlink.net/~dannewberry/_wsn/page2.html

If you're dealing with a light, fast varmint bullet, seating it DEEP into the case is the way to go for best accuracy--especially with factory chambers. You can totally traverse the vibration whip cycle with about .24" of seating depth adjustments from the beginning depth(.12" deeper, .12" farher out). This .24" figure is approximate, and is based on reviewing various targets of my own, and those of others where depth tuning of the bullet was tested. Suffice it to say that it doesn't take but about .003" to .005" of seating depth change to really move the bullet on the vibration whip.

We can discuss this more at length if you're interested, just state your thoughts and we'll see where it takes us...

Dan

Ah, barrel harmonics. The longer I chase a single-hole group the more convinced I become that it's all (or nearly all) about the barrel whip.

When we vary powder, bullet jump or even bullet shape within a given weight, isn't it true that what we're really trying to control is the point in the vibrational cycle at which the bullet leaves the barrel? Whether you believe a barrel's "sweet spot" is at one extreme of its whip cycle or perhaps at dead center, I think that's what we're all seeking.

Continuing on this whip cycle question, most of us are trying to understand and control it from the chamber end of the rifle. But Browning's BOSS system takes the opposite approach. Instead of trying to "tune" a load so the bullet consistently leaves the barrel at a consistent point in the whip cycle, the BOSS seeks to tune the whip cycle to match the load. I'm intrigued by that concept if for no other reason than it's a very different approach to our "problem."

And what about the barrel pad or hump that Remington for years built into its gun stocks (and may still put in for all I know). Wasn't that an attempt (and successful by some accounts) to either dampen or shorten the whip cycle out near the muzzle? And what about the tuning devices that let the shooter put variable amounts of upward pressure on the barrel out near the end of the stock?

Since you've obviously pondered these things a lot, let me ask this: Aren't there industrial-strength scientists with techniques and instruments capable of measuring and understanding rifle barrel harmonics? Seems to me we're all gonna be chasing our tails for a long time until we start learning some truths about this mysterious whip cycle. It may turn out that the "truths" change with different calibers, different weight or contour barrels, etc., but I have a feeling that's where our holy grail lies. Maybe my "revelation" is old hat to some of you guys, but I still see a lot more written about super new powders, super new dies and super new scopes than I do scholarly studies about barrel harmonics.

I did follow the link posted by Dutch in the smoke ring thread and that article was quite enlightening. I did a web search on the names of the two authors and found that they indeed did file for a patent on a device (system?) to adjust barrel harmonics, but I couldn't determine if it was ever marketed. Anyone know?

So, am I nuts, or is the science of barrel harmonics something that's been vastly overlooked, at least by the average accuracy buff?

KF,

Take a look at Jameister's "watermelon seed/smoke ring theory" thread. Much of what you mention is mulled over there. Brent Moffitt shares some text from a Harold Vaughn volume, "Rifle Accuracy Facts," and in so doing will likely sell a few books for the now celebrated Mr. Vaughn.

Basically, you're right with everything you mention in your last post. Your post was well thought, and well written. We are indeed talking about the pursuit of the load that not only hits that "node", but hits it predictably--not just today, but tomorrow, next week, and next year. That's what I believe an OCW load can do better (the predictability part, I mean) than a conventionally developed load.

I think the BOSS system is probably a godsend to those of us who don't handload, but superfluous to those of us who do. I'm a very firm believer (who-da thunk it? ) in the OCW load process, which entails what I call the "depth tuning" of the final product (bullet seating depth adjustments) to find that node you mention. This will yield the best possible powder charge and bullet seating depth.

As you may know, I believe the perfect powder charge doesn't change that much--if at all--from one conventionally built rifle to the next. I think the notion that "different rifle's like different amounts of powder for the same basic load" has proliferated precisely because folks use different seating depths for their load development. This naturally leads them to different conclusions as to how much powder their rifle "likes."

But back on the Varmint Hunter article, I believe that beginning with a preconceived seating depth, and then altering the powder charge to make that depth work is a lot like beginning with a particular engine ignition advance and then swapping out pistons until you find the engine's "sweet spot!"

Take care,

Dan

Dan:
This topic has spawned a lot of response, some good and some bad. I don't have the capability to do this, but it might be nice if someone (read, YOU) could compile all the threads into a single file that could be accessed or downloaded.

I just got reminded that I only have four monutes left so...

Seems like most benchrest shooters find that the optimum seating depth is dependant more on the barrel (throat dimensions, etc.) than the charge they use. They'll say that a particular gun likes this seating depth regardless of the charge. This was also borne out in experiments at the "Houston warehouse". With this in mind, starting out with dialing in the seating depth makes sense. I think that factory chambers and slender barrels changes things though.