Quote from dgabriel:
I don't believe that the specialist is permitted by NYSE rules to do what you feel he is doing. If there is a bid for 50 and you hit the market sell, and if your order arrives before anyone else's and before the the bid is pulled, the specialist is obligated to fill you at the quoted price, even if it is his bid. What does the tape show when this happens?
If you find that a specialist routinely does this and you have the tape to back up your suspicions, then you may file a complaint with the NYSE. Your broker can also petition the specialist directly for restitution.