The StA409 continues with Helghast weapon design tradition, favouring volume of fire over accuracy with a high rate of fire. While the Keyzer features a smaller magazine than its previous incarnation, it is also vastly improved in terms of recoil and bullet spread. The new motorized drum magazine also allows for a faster reload, since the magazine lock will automatically move into place when the magazine is pushed in. Attachments are a new addition for Shadow Fall, allowing for optics and underbarrel attachments to be equipped. The StA409 can be equipped only by the Assault class in multiplayer.
The StA409 can be equpped with the usual array of weapon sights, including the Holographic sight and the ACOG, whilst coming with a red Dot-Laser as standard. The StA409 comes equipped with a vertical fore-grip as standard, although an underslung shotgun , as well as an underslung grenade launcher will become available for use once unlocked. In the campaign it can be found with the E-Stun Missile attachment.