Could be a seal issue, that would explain the loudness,buzziness and hold sensitivity.A seal not doing it's job, makes for a nasty springer.
My Valuemax averages 739 fps with 14.3 grain Accupells and 741 fps with Benjamin cylinders.It is not broken in yet.First shot with both pellets was about 30 fps faster than remainder.I will try JSB and H&N pellets next and do some accuracy testing from bench rest.So far so good.