A catcher, in combination with a firearm having an ejection port, for receiving and retaining expended magnetically attracted shell casings through the ejection port as the firearm is discharged. The catcher includes a hollow housing having a plurality of rigid walls, and retainers. One of the walls has an opening in communication with the ejection port when the catcher is mounted to the firearm for receiving the shell casings. A seal is attached to the housing at the opening and surrounding the opening and provides controlled release of pressurized ejection port gas from inside the housing as the firearm is discharged such that noise and flash as a result of escape of the pressurized ejection port gas is reduced or eliminated.