The basic notion is that for every load recipe (cartridge, bullet, powder) there is an optimal amount of that powder which will ignite and burn most consistently. I call this the Optimal Charge Weight, or OCW. An example is the 270 win. using 130 grain bullets and IMR 4350. The OCW is 55 grains of the 4350. I discovered this via the method I'll outline below, but I note that Winchester seems to have discovered it long before me. They used to use this exact charge of IMR 4350 in their factory 130 grain loads.
What I'm saying is a bit controversial. Most folks are of the school of thought that all rifles are different, and the perfect charge of powder for one will not be the same as for the next. That's true to a degree, but I believe that the fine tuning may be better achieved with primer and seating depth variations, keeping the OCW fairly unchanged.

I will continue this thread with another post which outlines a sort of "modified Audette method" for finding the OCW for a given recipe.

My reason for continuing the thread with another post is that I don't want to lose this introduction if my post turns out to be a bit long.

Please stay with me here, and please do offer any criticisms and dissenting opinions, and reasons for such. I'm interested in opposing viewpoints, as well as the words of any of you who have perhaps been using a similar method of load development.

Creighton Audette used a method for finding the "sweet spot" of a particular load by shooting at a fixed point at 300 yards. His loads consisted of graduated charge weights, with cases, bullets, and primers being the same. He would shoot, in the 270 win example: 53.2, 53.5, 53.8, 54.1, 54.4, 54.7, 55.0, 55.3, etc...

What Audette looked for through the spotting scope was a "cluster" of bullet strikes in the vertical string on the target. In the above example, ideally, there would be a tighter cluster from 54.7 to 55.3 than in anything previous or after.

One problem with this method is that one must really be sure of his prowess on the trigger. A couple of pulled shots would spoil the whole test. Another problem is that the various charge weights would not necessarily string vertically at 300 yards. I think we have all seen load variations cause as much lateral movement as vertical.

I'm open to suggestions for improvement of this system, but here is my own method as I currently use it. It has worked for me so far, but that doesn't mean there isn't room for improvement:

I like to use graph paper with the 1/4" squares for targets for this purpose. The best aiming point is a black square, drawn by a marker. The best size for this square will depend on your riflescope's power. Set your scope to maximum power, and experiment with square sizes until you have one which you can *just* quarter at 100 yards (or 200 yards if you prefer to test at that range). You want the square to be big enough for you to see all four white quarters around your crosshairs, but small enough that there isn't a lot of wobble room inside the box.

You begin your load testing with all equal components: brass, bullets, primers, and seating depth. Make up three of each charge weight. In an example let's say we're testing Varget in the .243 win with the 85 grain Sierra bullet. I'm currently making the ammo for this very test, and some of you here helped with the parameters I chose. When I get to the range, I'll have three each of the following: 37.0, 37.3, 37.6, 37.9, 38.2, 38.5, and 38.8. I will of course clean the rifle between each three shot group, and foul it with one shot before firing the next three shot group.

I'll have in this example seven groups. Most of us would look for the best of the seven, and call it done. In some cases, we'd be right, but in others, perhaps not.

After all groups are complete, with called flyers noted (this should still leave two shots in good standing), we would now compare the *point of impact* of each group. What we are looking for at this point is not the tightest group of the seven. We are looking for the *three* groups which land closest to the same place on the individual targets. (Here is where the graph paper comes in handy). In some cases, the best group of the seven will be among this trio of groups, in other cases it won't.

If I happened to notice that I fired a 1/2" three shot group with the 37.0 grain charge, but the three groups which came closest to hitting the target in the same place were the 38.2, 38.5, and 38.8, I would still opt for the mean charge as my OCW: 38.5 grains.

In doing so, I may not have a 1/2 MOA load (YET! we'll get to the fine tuning later..) But what I will have is a load that is *resilient*. Such a load will be much more tolerant of temperature changes (even when using powders which aren't particularly noted for their temperature stability). A resilient load will also be less affected by minor lot to lot variations in brass, powders, etc.

I would much prefer a 3/4 MOA load which isn't finicky to a 1/2 MOA load that was.

Okay, I'm about done here. Thanks for enduring my verbosity.

Another advantage to the OCW method is that your charge weights can vary slightly above and below the mean charge, and you'll still have basic accuracy.

And when your shooting buddies decry the lot to lot variations of components, you'll have no worries.

When I identified the OCW for my 270 using 130 grain bullets and IMR 4350, I tested using WLR primers. I did in fact shoot the best group of all tried with the 53.8 grain charge. But 53.5 and 54.1 were not so good. The 54.1 grain group began a major deviation away from the POI of the 53.5 grain charge.

So I went with the 55 grain charge, and began testing other primers. To shorten the saga, I found that Federal 210's did the trick. The old Model 70 now shoots 1/2 MOA so consistently it's a sin.

As a final fine tuning point, you can adjust the bullet seating depth, or distance from the lands to really bring things into check. Most folks do all of this in reverse order, but I think there is merit in doing them this way. There is nothing whatsoever sacred about distance to lands. Folks often begin with a set length, and proceed with load development until they find a good load, and assume that their rifle just "loves" that distance from the lands...

Of course if you keep everything *just so*, and get downright anal about case prep, lot selection, etc, you can shoot tight groups with just about any charge weight in the normal range.

So there it is. If you're tired of lot variations and weather conditions playing havoc with your pet load, maybe it's time to redevelop, this time, with an eye toward the OCW.

A final point. When using this method with the small cartridges such as the .223 Remington, .2 grain variations would probably be in order.

Dan Newberry
(green 788)

From my own experiences each gun is it's own gun and they all have their own preference for both type of powder and charge weight.I have owned several guns of identical chambering and their most accurate loads in some cases were with the same powder but the charge weight for most accuracy varied considerably.Theories may indicate what charge weight could be best but each gun will tell you what is best in that gun.

thanks a ton for a very interesting post. Saved me from asking you to flesh it out specifically. This one I'm going to try.

So let me get this straight. With your method you just arbitrarily pick a seating depth and then load up some cases with varying powder charges, using about 0.3 grain increments, and go out and shoot them. You are not so concerned with group size, but rather with point of impact. If your gun and load is giving a 2" group at 100 yards with a charge of 75 grains of powder and similar size groups at 74.7 and 75.3 that is all right so long as the group centers are very close to each other. Right? Then you take that 75 grain charge and start fiddling with seating depth until it is giving 0.5" groups. That is the hope anyway. If the gun is built right and a premium barrel is used and the shooter is capable of 0.5" groups and bullets are used which are capable then that should be achievable. You were lucky with your 308 using the 168 SMK. If I remember correctly your worst group was 0.8". You must have been basically at the best seating depth already, to be getting groups in the 0.3" range.

My gunsmith told me his method yesterday. He said that he picks the bullet he wants to use and then seats them about 0.1" off the lands (again assuming his box is long enough) and then loads one shot at a time going up in powder charge until he is at safe maximum. Then he loads up some at the safe max charge and shoots a group. When he was working up in powder charge he was not shooting at paper. He was just checking for signs of pressure. Anyway he works his way out in seating depth about 0.010" at a time, getting closer to the lands. That way pressure will be decreasing instead of increasing. He said that his method works well. It is sort of like Gerard Schultz's method except my gunsmith starts with the bullet seated deep and Gerard starts with them seated out as far as possible. Your method is much different and accomplishes something totally different in that you are looking for a powder charge that is as you say flexible. There are many ways to skin a cat.

My big concern was that there was only one good seating depth and if that seating depth was beyond the length of your magazine box then you were screwed. It is looking like there may be several equally good seating depths for most guns using most bullets. Perhaps the benchrest guns and guns using vld type bullets are more limited and do need to be at or into or very close to the lands. But it is sounding like that for most bullets, especially in rifles chambered with a reamer that cuts a parallel throat instead of a tapered throat, there are a few sweet spot seating depths. I am not sure which method I will try next. Rufous.

Jim Borden suggests something similar. It's all based on barrel harmonics and the 'whipping' of the barrel. You will generally find the best load at the extremes of the whip, since from a 'time/space' perspective this is where you have the largest window.

I'm not as smart as him and wish I could describe it better.

Michael

I believe you can tune to the stable portion of the whip by changing OAL in most cases. You would do this only after finding the powder charge that, with a 1% increase or decrease in the charge weight, shoots to the same POI. Rufous, you have it pretty much right. And you're right to observe that it takes a pretty decent rifle to take advantage of such a loading method. Otherwise, you'll be looking at an indecipherable mess...

I think if the groups are 2" in size, it might be beneficial to change primers and test again. I first began testing IMR 4350 in the .270 win using Winchester WLR primers. Groups were over MOA. By switching to Federal GM primers, I reduced these groups to around 3/4 MOA, and the test netted an optimal charge of 55 grains of IMR 4350 (with the 130 grain bullet) as the optimal charge of that powder in that application. Turns out that Winchester had already discovered this thirty years ago, and used this very charge of IMR 4350 in their .270 130 grain loads for years.

Let me know if you try it, and how it goes. If you begin with an accurate rifle, and a decent powder, bullet, and primer, things should work out well for you...

Dan Newberry
green 788

I think there is more than one sweet spot and more than one seating depth that will do the job. We just usually find one and call it good. Barrels are like string intruments, you can have several of the same notes on the same string only an octive apart.

Barrels also vibrate in a circle not just up and down or left to righr. Anyone ever play with a rope? You can make it have one, two, three or more rotating points the faster you twirl it. Just like a sine wave, the faster it goes the more "humps" it has AND the more "nodes" it has. Get the barrel to vibrate at the right harmonic where the node is at the end of the barrel and "asleep" and the bullet will exit at the same point every time. Of course, that's the hard part of reloading.

One thing I do when I'm load developing is look for the groups to go from horizontal dispersion to vertical dispersion or vice versa. At that point the node has basically changed directions by 90 degrees. When that happens, many times but not always, splitting the amount of charge increase by half will produce a round group which is what I'm looking for, then changing the seating depth in or out a few thou will start the round group going two directions, either smaller or larger. If I seated toward the lands and the group got bigger then I just would go the other way with the seating.

It doesn't take much for the group to get to the one hole stage from there. You just have to try the load in different conditions to see if it will hold that level of accuracy.

You want anal, I'll give you anal. I went so far as to use a weight scale when I seated and if the case didn't fall withing the parameters I set it was put aside. I ended up with 7 cases out of 50 that were as close in weight, length, inside volume, neck thickness, etc as you could get. I ran them over, under and through every measuring device I could get my hands on. I even rolled them and marked how they stopped.

The rifle I was shooting wasn't a benchrester but the centerline of the bore and the bolt face were parallel and perpendicular. It's called blueprinting or trueing nowdays, but back when I had it done that was part and parsel of doing a rebarrel. Those seven cases would make one hole every time I shot them with that load but I sweated blood to get that. It was a learning experience, an intellectual excercise, a testing platform and a lot of hard work. I wouldn't do it again but I'm glad I did do it.

That rifle shot 1/2" or smaller groups all day with just about any thing I fed it until I wore out the barrel. It's long gone but a happy memory.

The best part of this sport is we can get to the same final point through many ways. I don't think there is just one way or the highway.

Everyone has a contribution to make, you just have to be smarter than the bullet to use it. So far every one on this thread has given me a great deal of information to mull over and ruminate on.

I thank you all.

Makatak