Heckler & Koch PSG-1

The Heckler & Koch PSG-1 is a short-range sniper rifle used by the Tokonosu prefectural police Special Assault Team(S.A.T.). It is used by Rika Minami while she is stationed at Tokonosu Offshore International Airport.

Overview
The PSG-1 is a sniper rifle. It is manufactured by Heckler and Koch. It is used by many armed services around the world, but mostly European, and particularly anti-terrorism. The way it was found in the manga seems pretty legit as Rika was assigned for anti-terrorism. In fact, real life SAT has several of these rifles in their arsenal, which explains how Rika was able to get one.

Plot
It is only seen once. Rika uses it to eliminate "them" on the runway to clear way for the airport. Although it is not clear yet, she might actually carry it around as one of her arms, if not her standard issue firearm.