The RUST Extended Magazine is a weapon attachment that allows players to modify certain guns with a removable additional ammunition feature. It provides an additional 25% on-use ammunition option for guns that are applicable. The extended magazine was introduced in the RUST Combat Update in June 2022.
Currently, this magazine can only be added to guns that have a fourth attachment slot, those being the Custom SMG, Thompson, LR-300, Assault Rifle, MP5A4 and Semi-Automatic Rifle. It may also be attached to the M39 Rifle despite the lack of additional attachment slot.
Players may learn them directly via researching or invest considerable Scrap into the tier 2 workbench tech tree. Extended magazines may also be found on most scientist types or as drops from military crates.