I believe that data is from their factory ammunition.
I know for their Load Data results they use a 24" barrel for the 7mm Rem Mag and a 26" barrel for the 280ai. Perhaps they use the same length same length barrels, respectively, when testing their ammunition. But I don't know how much more velocity you get from 2" more of barrel? Perhaps thats why there is a difference.
All I know is that if I didn't own a 7mm Rem Mag I would own a 280 or 280ai.
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