The HK22 Gun was the upgraded version of the Seeker Gun. The HK22 Gun fired out three closed seeker barrels at once. The seeker missiles flew slowly until they locked on to enemies, then opened up and homed in. Seeker missiles from the HK22 dealt more damage and moved marginally faster. Although the ammo was reduced from 25 to 20, 20 shots of the HK22 had equal power to 60 shots of the Seeker Gun.
- Due to a glitch that prevented enemies from taking damage for a fraction of a second, the Lock-On Mod was cut from the game, as the lock-on would cause all three seeker missiles to hit simultaneously and deal the damage of one seeker instead of three, wasting ammo.
- There are weapons in the real world that are called "HK," standing for "Heckler Koch", but the "HK" in "HK22 Gun" likely stands for "Hunter Killer," thus likely making this gun the Hunter Killer model 22 in formal terms. 
- Similar to the seeker gun, when collecting a Platinum Bolt with the HK22 Gun equipped, Ratchet's arm disappears.
- Seeker missiles do not affect enemies' health levels if they get hit with another seeker missile right after getting hit with one. Because of this, one should wait a second before firing another seeker missile on the same enemy.
- Ratchet & Clank: Going Commando (first appearance)