An anti-chop system for a pneumatic paintball marker that is automatically cleaned. The anti-chop eye system includes a transmitter and receiver arranged so as to sense the presence of a paintball within a breech using a beam of light. A moving member of the paintball marker automatically wipes at least one surface of the transmitter and/or receiver to remove contaminants such as paint, grease, dirt and the like. By automatically cleaning the anti-chop eye system, the reliability of the system is improved.