speed, power and accuracy

[model 70]

can someone clear up a few things?

why is it that the .220 swift surpasses the .22-250 in speed (and power?) when shooting the exact same wieght .22 cal bullets?

why do you hear about most long range shooters using the .308win instead of the 30/06 yet both can fire the exact same bullet with the '06 using more powder?

doesn't a bigger powder charge push the bullet faster and more accurately?