Abstract: A firearm receiver apparatus comprises a receiver body and a light emitting device. The receiver body includes a bolt carrier bore and a cartridge ejection port. The bolt carrier bore extends between first and second end portions of the receiver body. The cartridge ejection port extends through a sidewall of the receiver body and intersects the bolt carrier bore. The light emitting device is attached to the sidewall in a manner for causing at least a portion of a beam of light emitted therefrom to be directed through the cartridge ejection port into the bolt carrier bore.