Were the numbers we see on today's published dram equivalent charts arrived at by actual velocity measurements?

The reason I ask is that I have noticed that a 12 ga. dram equivalent load does not have the same published velocity as the exact same load in a 20 ga. For example, a 12 ga., 3 dr. - 1 1/4 oz., load is published at 1165 fps. The exact same load in a 20 ga. is published at 1185 fps.

If these aren't reported actual measured velocities, how were they derived?

SRH

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