drover,
Thanks for listing your objections.
Before going further, let me explain my methodology a little more. Instead of averaging the maximum velocities of ALL load data, I averaged only the fastest velocities from each company�s data for each cartridge. This provides the best idea of the potential velocity of each cartridge, rather than including data for less suitable powders.
I also wanted to compare pressures taken with the same type of equipment from each company, in order to compare apples to apples. Hodgdon�s top 40-grain velocities in the .223 were taken with copper-crusher equipment, while all their .204 data is piezo, so I didn�t include their data.
As for the 25 fps/inch adjustment for barrels longer or shorter than the standard SAAMI 24�, that�s pretty much the industry standard. But to be fair, I went back and averaged the results of handloads from the 22� and 26� barrels on my two present bolt-action .223�s, and the result turn out to be a slightly faster than when using the 25 fps adjustment, though the difference was under 10 fps. This tends to validate the adjustment.
I also went back and listed every present source of data I could find for 40-grain bullets in the .223, including the fastest velocities regardless of barrel length. I own all the latest manuals from Barnes, Berger, Hornady, Norma, Nosler, Sierra and Speer, but looked up Accurate, Alliant, Hodgdon, Ramshot and Vihtavuori on the Internet. Only Barnes and Norma didn�t list 40-grain bullets in the .223.
One anomaly stuck WAY out: The fastest listed velocity in Speer�s latest (14th) manual for 40-grain bullets was only 3557 fps. Even from the 22� barrel of their test rifle this seems very slow, since the next lowest velocity, 3674 fps, was from Hodgdon�s copper-crusher data. But Speer is one company that uses a pressure-barrel to determine max loads, then chronographs the data in a factory rifle. I don�t regard this as valid pressure/velocity data, but for the sake or your argument included it in the average, which turned out to be 3744 fps�which still averages higher than the top 40-grain velocity from all data for the .204.
You may find it interesting that the two companies that tested the .204 in 26� barrels and the .223 in 24� barrels, Berger and Nosler, list a higher 40-grain velocity for the .223, despite the 2� barrel advantage for the .204. (Oh, and the higher SAAMI pressure for the .204.) In the Berger manual the difference is 44 fps in favor of the .223, and in the Nosler it�s 45 fps.
Since the lowest top velocity I could find with 40-grain bullets in the .223 is Speer�s 3557 fps, I am very curious where you found two loads that averaged 3553 fps.
