Home Forums Reloading Big Game Rifles Conflicting Load Data

How do you experienced guys deal with conflicting data in load books?

I've been loading for a few years but haven't ventured beyond a couple of powders using Hornady bullets and Hornady loading data.

I recently bought a Lyman and Hodgdon manual an noticed the min/max charges listed are much different in some cases.

Example:
The Hornady Manual list the min/max for Varget using their 150gr SP interlock as:
- 35.9 through 44.9

The Lyman Manual for the same bullet is :
- 42.5 through 47.0

I see the same thing with the other two powders I've used (h4895 and RL15)

My gut feel is to stick with the more conservative Hornady data but I see quite a few loads listed in the "308 load thread" that exceed the Hornady data.

Thanks,
Mike

Max charges in manuals are good to work towards and past in some cases. Max in your rifle could be different than the manual, my rifle, etc. I have several loads that are above book max and I have no ill effects.


I don't load .308 Win but 44-45grs of Vargay seems to be a sweet spot with 168's so the Hornady data looks weak to me.

I'm loading 46.5grs of Varget in my 308 with 150gr bullet and ave velocity is 2875fps.I like the 150gr in the 308,they shoot a little flatter than the 165gr.My load for them is 45.5grs of Varget with ave velocity of 2725fps.

Funny...start to finish.

Wow..............

This isn't hard stuff.....rifle barrels, throats, bullet bearing surface,lots of powders,all differ...there are a million reasons for variations in data.You can write a book on this stuff.

Why worry about it?

Pick a range of normal velocities for the cartridge/bullet you're using in YOUR rifle. Start with conservative data,work up to that velocity level and where speed and accuracy and good case life meld together. Stop there and don't worry about differences in manual data.

If your velocities materially exceed what's "normal" for the cartridge,there is only one reason for it.

Mike,

Every time this sort of question comes up (and it comes up several times a year here) I repost this, which has appeared in a couple of books:

Many handloaders believe in a certain �conspiracy theory,� or rather an anti-conspiracy theory: They get pretty upset over the differences in loading data between the various sources available today. Many say they don�t find loading data �reliable,� and even believe the velocity numbers are exaggerated. I have even heard more than one handloader say he doesn�t �agree� with one manual�s data. This is much like saying he doesn�t agree with the gas mileage a neighbor�s F250 gets on the highway, just because his own F250 doesn�t get the same mileage.
Once in a while some of the anti-conspiracy theorists even suggest the loading-data companies should get together in a conspiracy, and standardize all their data so the poor home handloader doesn�t get so confused. The big reason for this, of course, is that these days an awful lot of handloaders have their own chronographs, so can compare their velocities with those listed in various sources. When a certain charge of Warp Speed 40-Million powder and a 130-grain bullet in their .270 go 100 fps slower than the Warp Speed Manual No. 3 lists, some handloaders see this as proof that something�s fishy.
Before we look at some data on loading data, let�s make a list of all the reasons the numbers in the Warp Speed manual might not match those of the �same load� shot from your rifle over your chronograph:
Your chronograph isn�t all that accurate. Modern �personal� chronographs are marvelous inventions, especially for the price, but light screens aren�t infallible, since not so oddly their results often vary according to light. Even with diffusers above the screens, readings can and will vary depending on the light from the heavens, even in chronographs costing far more than $100�though in higher-priced models the variations will be smaller.
In contrast, the chronographs used in ballistic labs are all top-of-the-line. Sometimes they�re not even available to home handloaders, or the price is too steep. The spacing between the screens is longer, making readings more accurate, and the chronographs are set up indoors, under consistent lights.
You�re not using the �same� load. Many handloaders assume that all 130-grain .270 bullets produce the same pressures. This is a hold-over from the days when just about all bullets were simple cup-and-cores, so did produce similar pressures, but today�s bullets vary enormously.
The main pressure factors are bullet material and bearing surface, the amount of bullet that actually touches the bore. Pure copper jackets or bullets tend to produce more pressure than the far more common gilding metal, a combination of copper and a little zinc, because copper is softer and hence �grabbier.�
Bullets with softer cores and flat bases also tend to produce more pressure, because the core can be �bumped up� in diameter by the powder gas, sealing the bore far more than a boat-tailed bullet, which tends to let a little gas slip by, especially just after it leaves the case mouth.
The list of factors goes on and on, but the main point is that you can�t substitute data for one 130-grain .270 bullet for another and expect identical results. More or less pressure produces more or less velocity.
Powder varies in burning rate from lot to lot. Powder makers can�t make each batch of powder identical because of variations in atmospheric moisture. The powders sold to handloaders, however, usually come pretty close because different batches are normally blended, so a new batch of Warp Speed 40-Million comes within 2-3% of previous batches.
Even then, however, how you store powder can affect burning rate. Let�s say you live in the dry West, storing powder in typical 1-pound canisters in your garage. Every time a canister gets opened, the powder loses some moisture. After a few reloading sessions, that powder is going to weigh less. When you weigh 60 grains of H4831 six months from now, there�ll be slightly more powder in the pan of your scale.
But the biggie is lot-to-lot variation. As an example, look at loading manuals that list both Hodgdon H414 and Winchester 760. These are exactly the same powder, made in the same factory, but are put in different canisters. (If you don�t believe me, ask Hodgdon, which sells both these days.) Yet many manuals list different charges of 414 and 760 for the same bullet in the same cartridge. The numbers won�t be vastly different, but they will vary some, and the differences are totally due to variances in manufacturing lots. When bullet companies orders powder for testing, it would be unusual to get 760 and 414 from the same lot. In fact, I believe the only loading data that lists exactly the same data for both powders is Hodgdon�s.
Primers and brass also make a difference. Many handloaders only differentiate between standard and magnum rifle primers, but even among �standard� primers there�s enough difference to result in a 5% difference in pressure, resulting in about a 2.5% difference in velocity. And yes, there are even differences in primers from lot to lot.
Brass varies in weight, with heavier brass producing more pressure and velocity. Even the precise size of the flash-hole in the brass has some effect.
Your barrel is different than the test barrel. It doesn�t matter whether barrels are factory or custom, they all vary slightly in bore dimensions. Even the test barrels used in pressure labs vary somewhat. They�re required to match SAAMI (Small Arms and Ammunition Manufacturers Institute) dimensions, but those dimensions are not exact, just within a certain range.
One lab technician told me that each .0001� (one ten-thousandth of an inch) of bore diameter changes pressure about 1000 psi, about 2% in a typical modern rifle load, for about a 1% change in velocity. (One old ballistic rule is that any change in pressure also changes velocity about half as much. The variation differs slightly with the powder type, but the rule is still generally valid.) This means that if your .270�s bore measures .2773� instead of some company�s .2770� test barrel, it will produce about 3% less velocity--about 90 fps in a typical 130-grain load.
Since bore diameters CANNOT be held to tolerances of .0001�, even test barrels produce different pressures and velocities with the same load. In fact, it would be a major miracle if they did not.
Now, let�s look at some numbers from those anti-conspiracy sources of loading data. I went through five popular sources, looking at 12 popular cartridges, picking the most popular bullet weight for each round and recording the highest velocity.
The sources were Alliant, Barnes, Hodgdon, Nosler and Ramshot. The cartridge/bullet combinations were .223 Rem./50, .22-250 Rem./50, .243 Win./85, .25-06 Rem./120, .270 Win./130, 7mm Rem. Magnum/160, .30-06/180, .300 Win. Magnum/180, .338 Win. Mag./225, .375 H&H/300 and .416 Rem. Magnum/400. (The 85�s were picked in the .243, rather than 100, because the heaviest 6mm bullet Barnes makes is the 85-grain TSX.)
Almost all the test rifles had 24� barrels, but for the rare exceptions I adjusted the top velocity by 25 fps per inch. Finally, I added all of each company�s top velocities into a grand total. In order, from fastest to slowest, here are the results:

Nosler--36,959.
Alliant--36,681.
Barnes�36,642
Ramshot�36,571
Hodgdon�36,491

The difference between the highest and lowest velocity totals is 1.3%--40 fps in a typical 3100-fps 130-grain .270 load.
Now, of course there are anomalies in data from different companies, especially if we pick out a certain bullet weight and powder. The anomalies are the same kind of minor glitches that occur in any major collection of test data, but overall there�s a remarkable agreement between the different companies.
Also, despite glitches in the data, I couldn�t find any evidence that any single company dominated in �fastest velocity for a cartridge/bullet combination.� Every company listed the highest velocity for at least one combination, just as every company listed the slowest velocity for at least one combo.
Just for fun, after going through all those numbers, I also gathered a few of my old loading manuals from back in the day when almost all bullets were cup-and-cores. Back then some manuals lumped all bullets of a certain weight together, because there wasn�t the wide variety we have today.
The manuals chosen were the Speer No. 6 (my very first loading manual, published in 1964), the Hornady Vol. II (1973), and the 2nd printing of Hodgdon�s 25th (1987). One of the most interesting things turned out to be the barrel lengths in the test rifles (and many were rifles, not just pressure barrels). Hornady used barrels from 20� to 28� just in the rounds selected for the data-gathering. Speer�s varied less, from 22-25�, while Hodgdon�s were almost all 26�. Muzzle velocities were adjusted for different barrel lengths in the same way, at 25 fps per inch.
Interestingly enough, Hodgdon listed data not only for their powders but IMR and Winchester powders, even though Hodgdon didn�t own those brands back then, as they do today. Also interestingly, the fastest velocity listed almost always came from Hodgdon powders. This manual, by the way, only lists bullet weights, not make, and sometimes lists a range of weights, such as 154-162 grains in 7mm.
Not all cartridge/bullet combinations from my �modern� list were available from the older manuals. The .416 Remington Magnum didn�t exist when any were printed, and the .223 Remington wasn�t listed in the Speer manual, even though it was introduced in 1964. Speer also didn�t make a 225-grain .338 or 300-grain .375 (and still doesn�t make a 300 .375). So only seven loads could be compared, instead of 12.
Even though only three manuals and seven cartridge/bullet combinations were included in the data, overall muzzle velocities varied 3%, as compared to 1.3% in the modern manuals. This indicates that modern data is a lot more consistent, even though bullets didn�t vary as much back then.
The major reason is that pressures were often estimated in those days, by the same methods used by some rather backward handloaders today. Loads were �worked up� by judging bolt-lift, seeing if primer pockets stayed tight, or other seat-of-the-pants methods that have since been proven erratic, to say the least. This helps explain the very high velocities listed for 130-grain bullets in the .270 Winchester: 3200 from Hornady (24� barrel), 3180 from Speer (24�), and 3213 from Hodgdon (26�).
Contrary to popular belief, there is a lot of agreement in modern loading data, mostly due to the standardization of SAAMI and more accurate methods of testing pressure. No, the data will never totally agree across the board, just as your F250 will never get exactly the same highway mileage as your neighbor�s, even if they�re supposedly identical pickups made the same year. But if we pay attention to details, today�s handloading data really can help us produce more consistent and safer handloads.

Mike, a change in brass can vary your pressures by as much as 8k psi. In a 308 sized case, that can be around 2 grains of powder.

Just because two different manuals list the same bullet and powder, doesn't mean it's the same load. Brass and primers also effect pressures, so it's important to pay attention to how all the components work together. If the rifle is new to me, I'll start on the conservative side, trading a little more lead and powder for data, and work up until the rifle tells me to stop.

I can understand the differences between different bullet companies and powder company manuals however I found a conflict between Nosler 6 and 7 manuals.

In 6 loading for the .308 win 150 gr Partition it lists Varget with a max powder charge of 48.5 grains at 106% load density. In 7 it lists the Varget with a max powder charge of 46.5 grains with a load density of 102%.

The other powders listed are the same in both manuals. So is the barrel manufacturer, primer and case. So I am assuming that they used the same data in both manuals with out further load testing. Which would be logical.

Why the change in the Varget load? Could it be the introduction of the E-tip?

Your thoughts would be appreciated

Banko32

First off, you know this but for the OP, reloading manuals don't give load data for a single bullet like the Partition, they give it for a weight class of different bullets aggregated. For Nosler, 150's and 155's. So you're basically stuck with the most conservative bullet in the bunch, in other words the min/max data that apply to the bullet that generates the most pressure with a given powder charge.

I don't know the answer to your question on the E-tip, but it's a good guess since it has a longer bearing surface and as MD pointed out, that's one of the things that increases pressure.

As far as the OP's question, I liked Bob's answer best--just look at the velocities since velocity = pressure. Find a load that's within the published velocity range taking into account differences in the length of the test barrel and your barrel, and you'll be good to go.

That's exactly the reason. In fact, other data changed between the 6 and 7 manuals due to new bullets, and not just the E-Tip.

Thanks for the responses.

John I have your book "Rifle-Troubleshooting and Handloading" and read through the chapter you pasted a couple of times over the last few days. I've enjoyed the book and have learned much from it.

I just wasn't sinking in but I see now that even though the bullet/powder are the same, the primer/case for the loads in the Hornady vs. Lyman manual are different.

Up to now I've followed the Hornady guide pretty much verbatim but with components being harder to get I haven't been able to find exactly what I've used in the past and have had to venture outside of what I know.

Thanks again.