Plebian: You are right that many protocols and even the powder is an unknown factor. However, this is presented as a general statement that "... given an equally-loaded and identical load that has been fold-crimped, the roll-crimped load never seems to achieve the pressure level of a fold crimped load."
cpaspr: You are also on point, the conclusion does seem to be what we would expect.
Now would it also be expected if the premise instead were to read like this?
"... given equally-loaded and identical fold crimp loads that have been assembled in 2.75" and 3" hulls, the 3" loads never seem to achieve the pressure level of the 2.75" loads."
Here is an *example example of the alternate premise:
First and third lead shot loads on the page - both have the same data, both are fold crimped, but one is a 2.75" load and the other is a 3" load. The 3" load exhibits lower pressure and velocity.
https://www.ballisticproducts.com/VP53%20data.pdf*Note: This copyrighted data would not properly format, so an off-forum reference is shown.
To cut to the chase: What was not spelled out in the 2.75" Roll Crimp vs Fold Crimp example is simply the Loaded Length of the Roll Crimped load is longer than a Fold Crimped load. The Roll Crimped loads have a greater loaded internal capacity. So the comparison is not an apples to apples example any more than comparing the same data put up in 2.75" and 3" fold crimp cases.
For the differences between a roll crimp and fold crimp to be properly compared, the roll crimped hulls would have to be shortened. That way the finished loads would have the same internal loaded volume.
A loaded 2.5" roll crimped cartridge would have the same loaded internal capacity as a loaded 2.75" fold crimped cartridge.
