A few days ago, I mentioned that I had tried the OCW method, testing it against a load I already knew was a good one. I was shooting 150 grain Sierra bullets, pushed by 50 grains of XMR4064 in a '93 Mauser. The OCW process showed that my load was proper for that bullet and caliber.

Ssince then, I loaded 21 rounds, all at those quantities and at an OAL of 3.12", the maximum the magazine would hold. I took my press to the range with me and shot three rounds at the first target, walked up to check the group, and then came back to seat the next three bullets one-half turn (of the seating rod) deeper. I fired them and repeated the routine through all 21 rounds.

This routine allowed the barrel to cool somewhat (it was pretty cold up there!) and also let me see what was happening as it happened.

After going through the whole ball of wax, it turned out that seating the bullet 0.157" into the case gave the best accuracy.

Does this prove that the OCW method works? Maybe-- and maybe not, too. It does make it seem as if it works, but I really need to see more experiments like mine to be able to make up my mind.

Next?

Derald,

Thanks for using your time and material.

What you basically did by altering the seating depth was you tuned the load to match your barrel's harmonic node. You had already confirmed that your powder charge was optimized.

I'm convinced that the three three shot groups at 100 yards are the best indicator of the OCW zone. The wind will have little effect on these groups, and the round robin triangulated groups are a much better indicator of common POI than one shot at 300 yards would be, as is done with the Audette method.

Of course the common POI of the three three shot groups at 100 yards may not necessarily coincide with the best harmonic node of the barrel, hence the fine tuning--done by seating depth changes.

A properly developed OCW load is *not* harmonic dependent. It will shoot well regardless of barrel harmonics. However, by matching the load to the individual rifle's harmonic whip (via seating depth adjustments) you've simply made a good thing even better.

The Audette load is by design harmonic whip dependent, and less stable because of it.

If you're looking at a new load that you want to work up, the OCW method will let you get there with a minimal amount of material spent. Eighteen to twenty shots for the initial test, and a few more for the fine tuning. I'm convinced that the finished product will be more "resilient" than conventionally developed loads. Such a load should produce fewer flyers, and less POI change during temperature extremes.

Thanks again, Derald, for sharing your experience. You should have the utmost confidence in the load you've finished tuning.

Dan

For any who may be interested, here are the original test targets for the .223 Remington OCW load I developed. The bullet used was the Nosler 55 grain Ballistic Tip, and the powder was W748.

The third target square had two 30 caliber bullet holes already in it, hence the "X's."

The first square has a "fouler/sighter" in the box, and the three shots for the OCW test are at top right. You'll note as well that the 27.1 grain group had a flyer that went high and right--and off the paper in the photo. I was unsure whether I caused that flyer or not, and since I happened to have another 27.1 grain charged round available, I fired it into the group before continuing. It went into the same hole as the shot on the left. However, when the 27.4 grain charged group took shape high and right, I decided that the flyer had deviated toward that group. So even though the 27.1 grain group has three tight shots, it threw a "high pressure" flyer high and right--into the zone of the 27.4 grain charged loads. Therefore, 27.1 grains would not be a reliable charge to use in this application. A tight brass case, or other pressure raising factor would cause the shot to move high and right.

The OCW was 26.6 grains. You can see from the target that 26.3, 26.6, and 26.9 grains all printed within a 3/4" overlay. In later testing, the 26.6 grain charge has shown no tendency for flyers...



Velocity is around 3150 fps from my rifle's 24" barrel. I left the OAL at initial test length of 2.350" for the time being, but may depth tune later on...

Dan

I've been reading the OCW method's description very carefully, going through it several times.

Here are my initial "findings" :

1) There is nothing there that could be proved or linked statistically to the claimed "neutral harmonic load".

2) To claim that there is a "range of powder charges" where barrel vibration is tuned to a same "whip" no matter anything else, will need hundreds of tests, with different powders, bullets, barrels, etc, etc to be proved effective to a certain degree.

3) However, is a good and rational way to develop a load, powder wise.

4) The range or OCW "effective zone" is nothing new, in fact many high pressure loads show the same behaviour, because of the diminishing returns.

5) Benchresters knowledge is certainly abundant on the fact that there is an "unsensible zone", and they knew that for years.

6) The "round robin" is somewhat an issue in itself, as well as the shooting technique employed.

I'm sure that Dan will work hard to show the merits of his idea. Again I HIGHLY APPRECIATE his passion, and from fellows like him is where our sport could gain more value.

neutral harmonic load?

I would have to agree with you there, Gus. I don't make such a claim. What exactly are you referring to?

Further, I don't claim that there is a "range of powder charges" where barrel vibration is tuned to a same "whip" no matter anything else"

In a word, I'm FLUMMOXED!

Maybe we can clarify things...

Dan

Well, let's see...

Let me put up a sketch of a typical harmonic whip cycle for illustration...



What I was basically saying is that a properly developed load will have a powder charge that will ignite and burn with extreme consistency.

Normally, we "persuade" a load toward a stable portion of the harmonic node with powder charge alterations. Often, however, we move away from the most consistent powder charge, and toward a less consistent charge for the sake of getting the bullets to exit on a stable portion of the node. (The Audette "ladder test" will lead you straight to such a recipe as often as not).

BLR7 developed the load referenced by using my OCW load development method, and he therefore was able to identify the powder charge that was yielding the most consistent velocities. (I don't believe that chronograph data is reliable enough for this purpose, by the way, and even if it was, the loads must be shot to gather such data, so it would seem to me that the target is the ultimate and best indicator of the OCW zone).

BLR7's load shoots consistently enough that it does not need a good harmonic node to perform. His seating depth adjustments shows that; no matter where he moved the seating depth to, the bullets still grouped well. Some of the short arcs would indicate that the bullets were exiting on a "fast" or "unfriendly" portion of the harmonic node, but nonetheless they did not print long strings on the target because they had very tight velocities.

So basically, a well developed load--one which uses the optimal charge weight of powder--will not be harmonic whip dependent.

Of course you can make a good thing even better by "depth tuning" the load, such that those extremely consistent shots do in fact exit on a "friendly" end of the harmonic whip. And then you'll have a truly optimized load indeed--the best of both worlds; a load that ignites and fires with extreme consistency, and also one which leaves the muzzle on a good harmonic node. Such a load is very forgiving of pressure changes induced by odd components, weather, etc.

I'm always willing to discuss things, so feel free to post any other concerns you may have...

Dan

Gus,

I think I just figured something out...

I shared an email exchange in another post, one which I had with Paul Box at Sierra Bullets.

In his reply to my question regarding "universal load recipes," he implies that some recipes just seem to create the correct harmonic whip of the barrel to group well.

I can understand your taking exception to that implication--and I do myself.

As mentioned above, I contend that these recipes do not need the advantage of exiting the muzzle on a good harmonic node. By virtue of their uniform velocities, they simply "beat the odds" and group well no matter where on the harmonic whip they exit.

Maybe that will clear things up some...

Dan

Dan,

I'm going to do some testing at 300 yards using the round robin technique, but I'll shoot three 3round groups at each load increment tested which will be 1.0 gr apart closer to max.

I'll put up four targets and shoot three groups on each one.

If I can't find a load to shoot well in 1 gr steps, it won't prove resiliant enough for me anyway.

The first load I tried with this bullet (178 A-Max, RL25, 300 Ultra) was a five shot .78 moa group at 300 yards with the load seated short, but these will be seated right on the lands to start development.

I'll keep you posted as to my results. I'm going to try the round robin method to see if the last round of groups would indicate my barrel needs cleaning and also to confirm the first string of groups at the same time I'm out. First time I've done it like this, so it should be interesting.

I'd like to test my daughters 243 in the same way to gain a little more insight into the methods here as well, if I have time I'll check it too.

Thanks Brent... Please do let us all know how things go.

If you have some Hornady bullets for your daughter's .243--say the 58 grain VMAX or the 75 grain VMAX, I believe that IMR 3031 in 39.8 to 40 grains for the 58 VMAX and 39.0 grains for the 75 grain VMAX will do the job...

Take care,

Dan