I have yet to fire a factory round that came within 75fps of their claim and most of them were more than 100fps slower.
Some rifles shoot fast, some slow because of differences in chambers and barrels. If you handload you can taylor your loads to the rifle and get the velocity quoted in loading manuals, even from slow barrels, but not necessarily with the suggested powder charge. Factory ammo has to be safe in all guns. They load to get the advertised velocity from faster guns. If they load to get that velocity from slow guns, those loads would be over pressure in fast barrels.
Some of my guns will get right at published speeds, some slightly faster, some slower. It is because of differences in individual guns, not the ammo makers.