This is a sentry gun, sort of like those used in modern FPSs. There are very few n-gons, mostly around the circular components, and is nicely modeled, using quads.
It is a triple-barreled gun mounted on an octagonal ring, with a tripod underneath, and is easily animated/rotated to suit your purposes. As to the magazine, it is located on top and to the side of the gun. This can be utilized in games and animations, as you see fit.