The present invention provides for a firearm including a buttstock defining a first bore extending along a longitudinal axis and a receiver coupled to the buttstock. The receiver defines a second bore extending substantially parallel to the longitudinal axis and in fluid communication with the first bore. The receiver also defines an ejection port transverse to the longitudinal axis. The firearm further includes a bolt carrier disposed in the second bore and moveable relative to the receiver along the longitudinal axis between a firing position and a rearward position. The firearm also includes an expulsion device at least partially disposed in the buttstock for flowing air through the first and second bores and out the ejection port as the bolt carrier moves between the firing and rearward positions.