Thread: “Manufacturer” load data

Why do we see so much variation in load data between “manufacturers”? One manufactures the bullet, the other the powder.

An example. Speer 130gr HP in .308 Win, ADI AR2208 / Varget. Speer don’t publish a pressure figure, ADI does.

Speer’s load data maximum is 47gr for 2,954 ft./sec.

ADI’s load data minimum is 47gr for 2,975 ft./sec, and has a maximum of 50gr and 3,130 ft./sec.

How? Why? I’ve never understood this kind of variation. Any sage reloader lore that can explain this phenomenon.

I suspect when you look at Speer data, it might be skewed in favour of Alliant powders, as they are part of that same conglomerate.

Different lots of powder, different brass, different pressure testing equipment, perhaps even different criteria for determining the maximum.

ADI/Hodgdon tend to use Winchester brass for 308 which is really baggy vs the Federal that I assume the Speer data uses (again, same conglomerate).

Greetings @Flyblown and all,
In the example quoted the velocity for 47 grains is close to the same between the two data sets so pressure will also be similar. A fair bit of compression will be needed to shoehorn 50 grains in the case so this is likely the reason for the difference. In other cartridges the data may be based on different pressure levels as is the case with some .223 data and the construction of the projectile can raise pressures even with the same weight of the projectiles and cartridge. Barrel interior dimensions may have tightened for the later PSI test barrels, resulting in higher velocities for the same charge and projectile. Once again the latest Hodgdon .223 PSI data seems to show this.
How does the average handloader deal with this? Working up using a chronograph is essential. Selecting data for the projectile you are are using or as close as possible is also essential. Making sure that your components like case volume and make is also important. A few years back I tested the Speer 125 grain TNT in my .308 with a 20 inch barrel. I used BM8208, AR2206 and AR2206H with 47 grains as the charge. Velocities were right on the button with the Hodgdons/ ADI data once barrel length was factored in.
Finally I dug out my tattered Speer No 9 Manual from the 1970's Their max load with the 130 grain HP and the slightly faster IMR4064 was 49 grains and 47 grains produced 2,943 fps in a 22" barrel.
GPM.

Different attitudes to risk, different legal advice and legal jurisdictions.


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Because the manufacturers have no control of their products after they are sold, any load data they publish must always be on the cautious side to allow for the idiot factor that exists. The published loads will produce a satisfactory result that will do the job. Optimum results can only be achieved with careful development by knowledgeable handloaders who take all the variables into account. That is the way it should be.