Nothing can (easily) be done about that. Valve made miniguns always transmit to all players to solve a bug with spin-up sounds never ending, which makes the heavy transmit to all players.
Well that poses a problem when someone gets mad and instead of leaving the server decides to shoot the ground forever while standing at the beginning of a hard jump. Because that solves things.
Sucks nothing can be done though. I'd suggest removing heavies but I know a few people like to conc as them.