Manufactures test their guns at the start of Series Production, as guns are sold and Problems are identified, improvements are made.
This years SCAR-H version can be shooting at the 330 FPS, but next years series could be running at the 420 or higher level.
In general this is not a bad thing unless you live in an area or country that has strict rules and laws regarding the import of AS Guns ( Guess where
), in these area the control measures can be so extreme that the guns are sold intentionally with Air Leaks to reduce the FPS Levels.