One GK-5 sentry droid was stationed on Mustafar during the Civil War, where it was recruited by HK-47 as part of his growing droid army.
GK-5, and other GK variants, mainly used carbines, bothan bola carbines, flechette weaponry, or any other heavy blasters, which often proved very deadly.
GK-5 was a small model; its successors included the GK-6, GK-17, GK-18, GK Oppressor and Doom Bringer.