Then there's this;
Most usualy, the ammo makers base their velocity figures on testing done with a "test barrel" which is attached to a fixture/tool, which is often refered to as a "universal reciever".
Some published loads in some loading-manuals use a simular device, but some are actualy done by shooting ammo through a real gun. If that's the case, then the questions become....what barrel length did they use, what was that particular gun's BC-gap, throat specs, barrel specs, twist rate, and does it's forcing cone match the one in yours?
All of the above effects the velocity of any given load. That, and often you'll find that when it comes to factory-ammo, there's also been a bit of optimism thrown in for marketing purposes.
You might find it interesting that one of my manuals list the results of testing which was done to determine the actual velocity of 45LC factory ammo. Taking the Remington 250 RNL "service load" as an example, it was found that it's actual velocity varied by 35 FPS when fired from two different Rugers and one Colt. The advertised velocity that Remington claimed could not be duplicated in either of the two Rugers, even though one of those had the longest barrel (7-1/2") of the three test guns.
That same manual also has the results of other testing done with actual guns that involved about any caliber that you care to name...and all with simular findings.
What all that tells me is that what Joe Miller said (that is "highlighted in red") is probably a lot closer to being "right" than is the published figures of this or that factory ammo.
Just sayin'.
DGW