The present invention provides for a firearm having a receiver defining a
bore with the receiver extending along a longitudinal axis. The receiver
defines an ejection port transverse to the longitudinal axis with the
bore defining an inner surface. The firearm further includes a bolt
carrier disposed in the bore and moveable relative to the receiver along
the longitudinal axis between a firing position and a rearward position.
The firearm also includes a shield longitudinally affixed to the bolt
carrier and movable with the bolt carrier as a unit between the firing
and rearward positions along the longitudinal axis with the shield
blocking the ejection port when in the firing position and the shield
sliding along the inner surface away from the ejection port when moving
to the rearward position in conjunction with the bolt carrier.