Abstract: A cover, or dust cover, for use in a firearm, the firearm being operable for firing a cartridge having a projectile and having a receiver portion including an elongated passageway, a magnetic reciprocatable firing mechanism operable to fire the cartridge, a charging handle connected to the firing mechanism, and a barrel adapted to receive the projectile after the cartridge is fired. The dust cover is adapted for movement and to substantially cover a portion of the passageway. A magnet is connected to the dust cover and is magnetically attracted to the firing mechanism such that the dust cover is drawn towards and substantially follows the firing mechanism as the firing mechanism reciprocates with respect to the receiver upon firing the cartridge, wherein the dust cover intermittently uncovers and covers the portion of the passageway as the firing mechanism reciprocates.

Abstract: A firearm is described herein. The firearm comprises a receiver assembly adapted to receive a cartridge, a bolt assembly including a firing device operable to fire the cartridge, a barrel adapted to receive the projectile after the cartridge is fired, and a gas assembly including a gas tube. The receiver assembly includes an upper receiver portion, a lower receiver portion, and an upper receiver cover. The upper receiver portion defines a longitudinal axis, and an indexing slot operable to receive the gas tube. The upper receiver portion includes at least one integrated exterior track extending generally parallel to the longitudinal axis adapted to slidably couple with the upper receiver cover and a plurality of interior tracks extending generally parallel to the longitudinal axis adapted to slidably couple with the bolt assembly. The upper and lower receiver portions are pivotally connected to one another.