Dan Newberry's Optimal Charge Weight system and the extra decimal point

[deepcore]

Plotting out the series of powder weights by following Dan Newberry's OCW system.
Since it deals with 1%, 2%, etc. increments...
What have other's who have used the system done with the hundredth decimal point? Round if off to the nearest tenth?
Ex 44.28gr becomes 44.3gr.
Or should one always round down (or up)?

Thanks

[FrankenMauser]

For OCW testing, I don't use percentages.

I figure out how many cases I want to load, and break the charge weight increments down accordingly.

For example:
Let's say I have enough cases to warrant 12 charge weights, and I have a load range of 44.0-48.6 gr.
That works out to 47 tenths of a grain, when including the 44.0 charge weight.
47 tenths / 12 increments = 0.39 grains / increment

Round it off to 0.4 grains per increment, and the list of increments looks like this:

1. 44.0
2. 44.4
3. 44.8
4. 45.2
5. 45.6
6. 46.0
7. 46.4
8. 46.8
9. 47.2
10. 47.6
11. 48.0
12. 48.4

That leaves me 0.2 grains short of the intended max, but is close enough for me.

If the increments leave me an odd number of extra cases, I'll add them to one of the mid-range increments (for extra testing), or add another between two existing increments with those cases (such as 46.2gr between 46.0 and 46.4).


However...
Over the last 2 years, I have found OCW to be a waste of time. I have had better luck by finding powders that reach 100% density with a near-max, max, or barely-over-max load. I use that to calculate a 95% load, and it is nearly always extremely accurate and forgiving. (Normal pressure testing loads are developed, and fired first, to determine the safe pressure range for that powder/bullet/primer/OAL.)

It gets me into a good load quicker (and more cheaply) than OCW.

[Doodlebugger45]

Over the last 2 years, I have found OCW to be a waste of time. I have had better luck by finding powders that reach 100% density with a near-max, max, or barely-over-max load. I use that to calculate a 95% load, and it is nearly always extremely accurate and forgiving. (Normal pressure testing loads are developed, and fired first, to determine the safe pressure range for that powder/bullet/primer/OAL.)

This is very intriguing. Is there a calculation you can do to find that powder and weight, or is it just trial and error? For instance, if I had a hunch that RL-22 might be good in my 7 mm mag, would I simply pour powder into case until it got to the base of the neck and then measure the powder weight to see if it was in the "safe" zone? That sounds simple enough. But what if I wanted to investigate RL-25 but didn't have a jug of that powder?

Your success speaks for itself obviously. But I wonder if there is a scientific theory that explains it as well? I realize you didn't imply that these were the only loads that are accurate. I have found some good accurate loads with relatively quick burning powders that were probably only 80% full. But, this method would indeed eliminate a lot of testing if a guy wasn't inclined to do it. Of course, there are a lot of times when the testing is the funnest part.

[Unclenick]

If I understand FrankenMauser's post correctly, he may use QuickLOAD or he may use something like Lee's VMD powder table (grains/cc) together with the capacity of his cases under his bullet seating depth to find 100% fill for any powders under consideration. With that list, he can go through load manuals and see which of those coincide with typical listed maximums. He then knocks those down 5% for his starting load.

Personally, I'd only be comfortable with a 5% margin if I'd already established a safe maximum with a particular component combination, powder included. 5% is a good number to allow for lot-to-lot variation if all other components remain the same. If it's a new (for me) powder and bullet or primer, I go for the 10% standard reduction and use Richard Lee's method of taking a starting charge to maximum in 5 equal steps. Those steps, as Newberry recommends for pressure, are 2% if I start 10% low.

To the original question, yes, round your hundredth's to tenths. Your scale is likely to err that much. Besides, if hundredths mattered to a load, it would be too touchy to handle changes in ambient temperature anyway, so I wouldn't be interested in it.

Personally, I use something close to Newberry's lower 0.7% step recommendation for the round robin which works out to 0.3 grain steps with medium power cartridges like .308. That's because you can walk over a sweet spot if the steps are too large. Newberry claims just 5 to 7 targets (15 to 21 shots, total) are usually enough to identify an OCW, and he works near the manual maximum, too. I've used up to 12 targets, as Frankenmauser listed loads for, just to see if I get more than one sweet spot, but 21 shots, plus foulers, on 7 targets is my typical run. I narrow the range initially using QuickLOAD and Chris Long's OBT calculator and shoot either side of one of the predicted sweet spot loads with the #4 target centered on the predicted load. The safe pressure limit determining steps still have to be taken first, but they foul the barrel nicely.

A quick note about loading for testing: I have long done test loading at the range, but have noticed the same loads that work well there being less precise when loaded in advance at home. Recently I read (Precision Shooting magazine, I think) a sort of reverse of that situation, where a fellow using a load put together at home that got great results, would get overpressure signs when loading it at the range. It turns out this has to do with the vibration of transport packing the powder down and reducing its ease of ignition.

What I do now is throw a few same-weight charges and fire them with and without tapping or with and without a drop tube to look at velocity difference due to packing. If I see too much (no hard rule here; depends on what the application can accept), I move on to a different load combination that isn't as touchy. This is on the premise that cartridge handling can either pack or fluff up a charge in the field, and I don't need any surprises.

[Doodlebugger45]

Thanks Unclenick.

I don't have QuickLoad, but I have studied the Lee VMD charts before. I was mainly just curious what method FrankenMauser was using exactly. Actually, in Newberry's writeup, he does kind of get into that same topic. He advises to pick whatever bullet you want to try and then to choose a powder that is more toward the slower end of the burn chart in the manuals. He doesn't say you have to use THE slowest powder listed, but slower powders mean heavier charge weights, which means higher load densities. That is the way I have done it so far. One thing that I tried was the 3-shot groups for each charge weight. I didn't like that at all. It's hard to pick out an obvious flyer in a 3 shot group. With 4 shot groups, it's more obvious and with the tried and true 5 shot groups I feel a lot more confident that I'm seeing real variations caused by the powder weights. When I find a sweet spot, I try 7 shot groups with smaller intervals between charge weight.

[deepcore]

Thanks guys.

Regarding Doodlebugger45s comment on flyers... I'm assuming using a one of those "sled" rigs to take the shooter out of the equation would help? Don't have one but was considering one to make things easier for sight ins and such. But was worried that all that recoil going into a stock without you to absorb the recoil is bad on the stock.

Unclenick... If I (can) only load at home. Is it possible to test somehow if a particular powder load is sensitive to packing and fluffing while at the range?
Tapping? Shaking?

[FrankenMauser]

I'm sorry. I shouldn't have said I have found OCW to be a waste of time.
What I should have said is:
I have found my 95% loads to work better with my reloading and shooting methods - for many cartridges. However, it works best with small or intermediate cartridges.
Part of the reason I prefer this method is because I am generally not a sub-MoA shooter. I have essential tremors, which causes me to shake continuously. For me, this skews Dan Newberry's OCW data to the point that it is often unusable.

If you still want to know why and how.... I'll clarify a few points-
I am considering buying Quickload again, but don't currently own or use the software. I also never really considered using the Lee charts. (Just didn't come to mind.)

To find my 95% loads, I do it the old fashioned way:
Method one:
Measure bullet seating depth.
Measure powder capacity of the case in question, at that seating depth.
Calculate the 95% load.
Load a string of pressure test cartridges - from 10% reduced max, or book starting load; on up to max at 100%.
I don't like compressed loads, as I've had a few "classic" compressed loads get very erratic and 'funky' on me. So, even if book maximum is slightly higher, I stop at what I determined to be a 100% load. (bullet touching powder, with no compression - before any settling)

Method two:
If I'm using components nearly identical to those listed in a manual, and the intended powder shows compressed loads at a max charge weight:
I load my pressure test increments from starting load, on up; watching as the charge slowly approaches 100%.
Once I determine the 100% load, I calculate 95%, and load some up (rounded to the nearest tenth of a grain).

For pressure test loads, I don't load 3-4 cartridges in any given increment. I usually load 2, at most. However, I use smaller increments, and ensure full case prep removes as many component variables as possible. Component consistency is crucial to the lower number of pressure test loads providing useful data.

Of course, prior experience with many of my powders comes into play. I know, for example, that IMR4064 and H380 compress before reaching max loads with nearly any bullet in .30-40 Krag and my 7.62x54R brass. If the burn rate seems like a good fit for the bullet in question, it's a good load candidate.

I also know that many of my powders are incapable of reaching 100% density in .220 Swift, .270 Win, and .30-06 with the bullet weights I shoot in those cartridges. However, calculating 95% of the max load for those cartridges usually gets me right in the ball park for a sweet spot.

Again, much of this is derived from prior experience, and 'gut instinct'. I have found AA4350 to be much more forgiving, and easier to find a sweet spot with, than IMR4350. As such, AA4350 allows me to do some charge weight variation testing (during initial 95% accuracy testing), while using fewer components than IMR4350 (which often requires a full second round of testing, based on the initial data). H4895 and IMR4895 are a similar situation. I have found H4895 to be more forgiving and generally much easier (and cheaper) to work with, than IMR4895.

You could say I'm using a modified OCW method. Since I do use the pressure test data in combination with the 95% charge weight data, it resembles OCW in practice. It's just that I'm putting most of my eggs in one basket, hedging my bets on that 95% load being close to the sweet spot.

Another difference in my method, is that I use only one target, and one point of aim. ...But I map out the hits on an identical target on my shooting bench. Rather than having to compare multiple targets with various groups, I have all the data on a single target I can overlay on the target mapped out with color codes and charge weights. It can provide for some real "Eureka!" moments.

Which brings me to yet another point:
With all the data on a single target, it is very easy to see sweet spots. As such, I've wondered if my 95% loads are a complete waste of components. After all, I had pressure test loads that covered that weight range. I keep loading those 95% loads when possible, though. I've just had so many good loads that were right at, or near, that 95% mark, that I can't bring myself to stop doing it.

Like all methods, it doesn't work every time. Sometimes it's just a powder/bullet combination that doesn't want to play together. Sometimes the butter zone happens to be at the low end of the weight range (which the 95% calculation ignores, other than pressure testing).

The cartridges that have shown excellent results with the 95% loads are:
.243 Win
.30-40 Krag
7.62x54R
.358 Win*
.220 Swift (with W780 - I have no other powders bulky enough)
.223 Rem*
.22 Hornet*
.327 Federal
(These were loaded for ladder testing by my brothers, but the final loads ended up being 95%.)

With potential loads that might require 30-40 test cartridges in proper OCW testing (due to a huge charge weight range), I can often get away with loading no more than 20 rounds for my initial testing; and less than that in round two, if I don't believe I have optimized the load, or want to play with seating depth.

When my 95% method doesn't lend itself to the load I want to put together.... I fall back to a different method of modified OCW testing:
I load the cartridges in small pressure testing increments (usually 0.1-0.2 grains, with a single cartridge at each increment), and use the same single-target and mapping method. It has gotten me two great loads for .30-06, one good load for .270 Win, a great load for .243 Win, and a wonderful reduced load for .30-06.

In the end, it boils down to the same principle of Dan Newberry's method:
I'm looking for a pressure tolerant sweet spot.

I'm really sorry about the length of this post. I'm always long winded...
If you have any more questions, or want to see an example of my "mapped out" targets, let me know. I don't have any right now, but could make up a quick example.

[Unclenick]

Frankenmauser,

Thanks for the extended explanation. That clarifies a number of things.

And now for some wind of my own that may or may not be of any use:

I have Lyman's #46 and #49 handbooks. The #46 has a fairly lengthy article on statistics for shooters. It's not a lot of fun to read, but it does of a method for deciding whether a group's improvement is statistically likely to be a real improvement or a random fluke. If the tremors are enlarging your groups randomly, that might be useful for distinguishing improvements.

Group size is determined by the two widest spaced holes. A two shot group has one possible size. A three shot group has three different pairs of two, so it offers three times as much chance to be larger. Four shots have 6 unique combinations of two, etc. So, the more shots you fire, realizing any two of them might equally have been the two that set the size of your group, the greater the chances are that two of them are at or near the gun's potential worst case for all shots with your particular load.

Shots/Bull  Combinations of Two
2                 1
3                 3
4                 6
5                10
6                15
7                21
8                28
9                36
10               45
11               55
12               66
13               78
14               91
15              105

The fly in the ointment to the above proving of a gun's potential is that some guns don't behave randomly as shot strings get larger. Some walk in one direction with temperature or fouling increases. Some change POI as they settle in the bags during successive shots. Some ammo is more temperature sensitive than others. Then there are a number of minor error sources that can accumulate during a long string: shooter eye fatigue, light changing, the sensitivity of the bullet to changing air density (with barometric pressure, temperature and humidity changes; mainly a long range issue).

The round robin concept is designed to average all those influences out. Each shot the first shot in its particular gun position on the bags. Each target has some shots fired from a more and some from a less fouled bore, and so on. There is certainly nothing to stop you from doing it all on one target, but you do need to keep track of which hole was the result of which shot, so a trend can be seen, if there is one. A spotting scope or optical sight with high enough magnification and brightness to identify each hole becomes an added necessity that the round robin avoids.

Given that the OCW method looks for three groups in a row with the same POI (and similar size is another good thing to look for, too), I think of that set as a nine shot group. Overlaying the three, as Frankenmauser suggests, is a good technique. Do it on a glass plate and you can use a backlight to see the whole thing.

That brings me to a particular value three shot groups have: Starting with a clean, cold gun, they will give you some idea what your gun does in the field with a first shot from a clean bore and two follow-ups. I like to round robin three targets with the same load that way, firing the three quickly, then stopping to clean and cool the gun. Three or more sets of three like that tell me if a gun and load are going to give me an issue with this. If so, I'll either work on the gun or not take it into the field clean.

The free On Target software is useful for identifying group size and center location. Just be sure to include something of known size in each target photo for the calibration tool.

Accurate publishes VMD's for each powder. Accurate also gives a tolerance for bulk density so you can work out the range of VMD's your particular lot might have. I wish they all did that. Their center number often disagrees with the Lee table some, and I assume that's because the Lee table represents measuring one sample. But the Lee table is a good starting place, anyway.


Deepcore,

You can play with shaking rounds to see if it has an effect, but I think mostly it just packs powder more, so I don't know how to guarantee you can duplicate the fluffiness of a fresh load made on the spot. However, if you always load at home, that's not a big issue as you'll always have transported the loads and vibrated them down a bit. Where loading at the range becomes an issue is mainly with benchrest guys doing to be able to use a small number of matched good cases over and over until they get an aggregate.

[FrankenMauser]

There is certainly nothing to stop you from doing it all on one target, but you do need to keep track of which hole was the result of which shot, so a trend can be seen, if there is one. A spotting scope or optical sight with high enough magnification and brightness to identify each hole becomes an added necessity that the round robin avoids.

As you pointed out, it is absolutely necessary to mark each shot, as the strings progress. I don't own a spotting scope, but I use my varmint rifle as a substitute. Set in some bags next to my shooting position, crank the magnification up, and I'm good to go. Out to about 150 yards, the 20x setting works well enough for me, even with .22 caliber holes (beyond 150 yards, there's a lot of walking, and 3-shot groups involved).

The target being marked at the bench doesn't have to be perfect, since I lay the shot target over the top of it later (which provides the true group sizes, and exact hit locations). So long as I get the marked hit location within a bullet diameter of the true location, it's easy to figure out.



...I'll see if I can dig up a Lyman #46, and take a look at that statistical analysis section.

[frumious]

This is really interesting information. I have just started shooting rifles (I have a Wby Vanguard in .308) and I am interested in developing an accurate load. I went over to the OCW website and had a read over there and I have a few questions:

1. How does one go about choosing a bullet weight? By just going with bullets of a weight that is "known" to be compatible with a given barrel's twist rate?

2. Dan indicates that once you find the 3 groups that resemble each other and you therefore determine the OCW, you can shrink the group size by simply playing with seating depth. That fits well with the barrel shockwave theory but it seems too easy. He also doesn't seem to see the need to set the bullet out close to the lands. What do you guys think?

3. If you don't let the gun cool between shots, but instead use a few fouling shots to bring the gun "up to temperature" and then shoot a shot every 30 seconds or so, what will this do to the usefulness of the method?

4. Does the OCW method work for pistols as well? Or is a 3-5" barrel shooting at a target 25 yards or less away a completely different animal with a completely different method that should be used?

-cls

[Win_94]

1. How does one go about choosing a bullet weight?

I use a twist rate calculator.

He also doesn't seem to see the need to set the bullet out close to the lands. What do you guys think?

Some bullets don't need to be close to the lands, it is the high BC bullets that do.

3. If you don't let the gun cool between shots, but instead use a few fouling shots to bring the gun "up to temperature" and then shoot a shot every 30 seconds or so, what will this do to the usefulness of the method?

Barrel temperature does not effect the test... Unless your rifle is in need of maintenance.
I'm assuming, you're assuming that a "cold-bore" shot has something to do with a cool barrel. Only by coincidence, does it.
A cold-bore shot is a shot taken with a perfectly clean barrel, free from carbon and copper fouling.

4. Does the OCW method work for pistols as well?

Yes.

[frumious]

Thanks Win94. About the cooling though...I am not mistaken. He references letting the gun cool, not cleaning the gun. So temperature does not affect the test?

-cls

[FrankenMauser]

Barrel temperature can definitely have an effect on accuracy - especially factory barrels, or other barrels from manufacturers that straighten them.

It is not uncommon for stresses in the metal to cause a barrel to warp during the barrel making process. The warping can come from simply removing metal, and letting existing stresses warp the metal; or they can come from heat created during drilling, rifling, or turning. Many barrel makers (particularly firearms manufacturers) will straighten those barrels before the final finishing processes are completed. The straightening process creates new stresses in the barrel - and those stresses are why temperature matters.

As a barrel heats up, it will warp, due to the stress created during straightening. This is usually seen as group-stringing, at the target.

That is why nearly every load work-up method you will ever see, has some kind of barrel cooling time period mentioned. It doesn't matter if the barrel is 125 degrees F, or 10 degrees F, so long as all the shots are fired at approximately the same temperature.

Since it is much harder to maintain a temperature above ambient (by firing shots to keep it there, or using a barrel heater), the simple answer is to allow the barrel to cool to ambient temperature between shots, or short strings of multiple shots.


I have seen some rather appalling heat-induced shot-stringing from various rifles. You never know what direction the stringing will go, until you test it in your rifle (if you need to know).

It's not as much of an issue, though, with barrel makers that don't straighten their barrels (such as Shilen, Lilja, and some others). They will still warp with increased heat, due to pre-existing stresses; but without the extra stress of straightening, they tend to perform more predictably.

[taylorce1]

I've used Dan Newberry's OCW method and even built a spread sheet to calculate the loads. I'm happy to share it with anyone who might want a copy just PM me an email. His method works pretty well but there are rifles that I own that just don't group well within 7-10% of max book load. Every rifle is different, some like plinking rounds and some like hot loads. I have a .270 that loves to be pushed, but my .300 Savage hates anything much hotter than starting loads.

[Unclenick]

Whether you have a barrel stressed by straightening or one stressed by rifling then contoured asymmetrically (like a Garand barrel, for example) heat can cause it to walk if it has not been stress-relieved. Douglas stress-relieves their blanks for an hour at 1100°F, IIRC, and that keeps them from changing afterward, unless someone decided to bend it. Cryo-treating causes enough grain structure change to help mitigate the stress effects, too, but its not as good as high temperature stress relief for that.

Howa, I think it is, suggests a barrel needs to be fired cold through a break in period to set the stresses and prevent it from walking as it otherwise would when it heats. If their observations are correct, one must infer some kind of stress relief occurs due to the transient stress of firing, perhaps akin to forcing a stressed piece of steel in your vice jaws to take a set by hitting the vice anvil with a dead blow hammer.

There is no reason a finished barrel can't be stress-relieved, but you need an oven that provides a non-oxidizing atmosphere during the heat cycle and some means of restraining the barrel so it doesn't wind up bent again.

Originally Posted by Win 94

Some bullets don't need to be close to the lands, it is the high BC bullets that do.

Actually, it's the other way around for the very hi BC VLD's. Read this from Berger on how they discovered their VLD's shoot better as much as 0.165" off the lands in some guns.

[Win_94]

Unless your rifle is in need of maintenance.

So temperature does not affect the test?

Everything written so far has reinforced my statement.

Actually, it's the other way around for the very hi BC VLD's. Read this from Berger on how they discovered their VLD's shoot better as much as 0.165" off the lands in some guns.

I actually phrased it wrong. I should have said, "Some bullets don't need to be [seated in the sweet spot], it is the high BC bullets that do."
But I didn't want to further confuse, and in order not to confuse I would have needed to elaborate... Since the thread was going off course, I didn't want to put any time into what I deemed would be deleted; so I left it as was.

[FrankenMauser]

Originally Posted by Win_94

Everything written so far has reinforced my statement.

Having a factory barrel that was straightened, and stressed, or having a barrel that was not cryo-treated; is not justification for saying the rifle is "in need of maintenance".

[Win_94]

Substandard rifles are either in need of maintenance or in need of being replaced.; load development with a substandard rifle isn't worth the effort.

[Unclenick]

The Precision Shooting Reloading Guide points out the obvious: If you have a gun that needs recrowning, bolt lugs lapped, stock inletting or bedding redone, or needs firelapping to correct sight dovetail indentation of the bore or other immoderate constrictions or distortions, then the most perfect load in the world won't shoot all that well in it. It will still shoot better with it than with the worst load, though. You just may need some statistical help to identify the difference in some instances.

Lots of guns seem to be in an inbetween state. They may shoot 1 to 2 moa and not seem particularly impressive, but then you still get situations in which they surprise you by responding unexpectedly favorably to a small change. My last standard weight M1A barrel, which shot around 0.75 moa with stick powder loads, would not shoot better than 1.25 moa with Accurate 2520, no matter what charge weight change or bullet positioning I used (this was for singly-loaded slow fire rounds, so I wasn't limited to magazine maximum COL). Then, on a whim, one day I tried deburring the case flash holes. Instantly, the groups shrank to 0.75 moa, same as the barrel got with stick powder loads. Deburring never did anything for the stick powders in that rifle that I could discern, but it made a big difference to the 2520 loads.

Another kind of example is in the old NRA Handloading book. Measuring bullet tilt relative to the case body, the A. A. Abbatiello sorted 829 rounds of National Match (later M72) ammo and he and another fellow fired a number of tests with it. They found, in a match rifle (probably a National Match '03), a coaxial round shot about 1 moa while bullets tilted about 0.004" off axis (0.008" TIR) shot about 2 moa. In a later test done in his book, Rifle Accuracy Facts, Harold Vaughn used the same degree of tilt, but, in a tight benchrest chamber in a bughole shooting "rail" gun (integral sliding machine rest gun; not one of those hyper velocity electromagnetic rail guns), only about 0.19 moa difference in group size occurred. So, it mattered a lot to the match rifle, but far less to the benchrest gun, which apparently aligned its bullets in its barrel pretty well, regardless of how they started out.

For an example of a gun that shouldn't have been able to shoot well, but did anyway, the first few paragraphs about Somchem's defunct load finding service in this old information on accuracy loading is an interesting tale.

Originally Posted by Win 94

"Some bullets don't need to be [seated in the sweet spot], it is the high BC bullets that do."

In general, the benchresters shooting short flat base bullets often claim to see a precision improvement with as little as 0.010" difference in seating depth, while Berger is showing it more like a 0.030" span to accuracy sweet spots with VLD's. That suggests high BC bullets are actually less sensitive to seating position than lower BC shapes. This may be a simple function of nose geometry. A long taper, needed to achieve a high BC, has to be moved a greater distance forward or backward to create an equal change in constriction of any round hole it is sticking into (like the freebore entry to the throat of a barrel). It therefore has to be moved more to have the same affect on the gas bypass that precedes bore obturation by the bullet. That degree of gas bypass in turn affects peak pressure (p.p., 44-51, Lloyd E. Brownell, et al, U of Michigan, 1965, In turn, peak pressure affects a bullet's barrel time, thereby tuning the bullet exit with respect to the phase of the muzzle's recoil-induced deflection (see Varmint Al's animated FEA's of this with a 500X exaggeration of the deflection into mode 3 ringing profile.).

In commercial barrels that have long freebores, it's not uncommon to find shorter bullets can't be seated out to reach the lands in the throat at all, much less get there without being too shallowly seated in the case neck (which the U of M study found also raises pressure). You may never find a identify a seating depth sweet spot for those short bullets in that kind of chamber, whereas, in a match chamber with a short freebore, you could. The whole business of tuning seating depth seems to depend on interaction between the chamber and bullet geometries, and is not something whose limits can be ascribed to just one factor or the other.

[Win_94]

That suggests high BC bullets are actually less sensitive to seating position than lower BC shapes.

That Berger needed to make a tutorial on how to find the "sweet spot" with their bullets to achieve better than "(poor accuracy);" flies in the face of your statement.
It is right in the link you've provided.

It can be difficult to get the VLD to group well (poor accuracy).

[Unclenick]

The statement VLD's are harder to load for accuracy is a general truism for a number of reasons (see Bryan Litz's book, Ballistics for Long Range Shooting), and seating depth doesn't address them all. It's just one of the things that has to be right for best accuracy with them. IME, most guns seem to have a preferred bullet weight and length range, and anything either side of that range is more difficult to get tight groups with, be they larger and higher BC or smaller and lower BC. The effort to get them to shoot may usually be aided by adjusting seating depth, except when bullets are so short they can't be seated anywhere near the throat without being outside of the case neck. So, I don't see any contradiction in what I said.

It's always a little hazardous to make blanket statements about firearms and load tuning, and I'm guilty of that myself at times. Somebody, somewhere always seems to have a gun that disproves the rule. I can think of one of my own. The M1A I used in matches in the mid 90's had a chamber specific to the rifle and M852 match ammo, which used the 168 grain Sierra. The 168's behaved normally and would shoot around 1.25 moa in an untuned load and could be tuned down to about 0.6-0.7 moa when I got everything right. But when I tried to load 155 grain MatchKings for short range matches, they were another story. They shot a very consistent 0.9 moa with any charge from 41.5 to 43.0 grains of Brigadier 3032 (a powder slower than IMR 3031—hence the name—and not dissimilar to Reloader 12 in some ways). I tried tuning seating depth with loads in the middle of that charge range. No change. It was OK accuracy for standing offhand and rapid fire bulls, but not the best choice for slow fire. It was better than the 168 would do over that kind of wide charge weight range, and it certainly was easy to load for in that sense. But it never quite came up to the tuned 168 grain SMK loads. Clymer, whom I believe first made the reamers commercially available for that chamber geometry, must have got that throat about right for the 168's. Such are the mysteries of the game.