IMO, that shows as much a variation of methodology of testing: barrels used, bullets used, primers used, etc. It's not uncommon to get a couple of hundred different FPS in velocity in factory rifles #1 and #2 with the same loads.
Nope, that dog won't hunt. See what happens when we use a more appropriate powder from the exact same manuals:
Speer #14........55gr...36.0/Varget...3655 fps
Hornady #6......55gr...34.6/Varget...3600 fps
Sierra #V.........55gr...36.1/Varget...3700 fps
Hodgdon 2008..55gr...36.5/Varget...3664 fps
Nosler #5.........55gr...35.0/Varget...3635 fps
H380 - 448 fps spread in max velocities.
Varget - 100 fps spread in max velocities.
Actually, it is rather amazing that Varget is so consistent. But then, it was designed to be.
Note that I never said that H380 didn't give good accuracy, afterall that is how it got its name. My own current .22-250 shoots 55-grain bullets very accurately with H380, giving aggregates in the .6s. But if you want to know your real velocity, you
have to use a chronograph.
.