Our game is ever so loosely based on reality.
And just to make a point.  An average 9mm bullet travels at about 300 meters/second.  A gun in our game that travels at around that speed is the Heavy Flak at 240m/s.  Another is the Gatling at 300m/s.  Most of are guns travel quite a bit faster.  .50 caliber sniper rifles are at about 800m/s.  The Field Gun was at 1200m/s and is now at 750m/s.  However, at the end of the day none of that crap matters because you're flying around in a virtual environment.  Reality is simulated and the way we perceive simulation is very different from how we perceive reality.
To put it simply, we are not a simulation.  The changes to the Field Gun can be compared to making it like it has the speed of a 9mm compared to before, fine, but I don't care.  It's about how it feels and how it affects gameplay.  I have that freedom to shape gameplay in certain ways because we are only loosely based on reality.  It's a good freedom to have because simulations are heavily constrained and imbalances are hard to fix.