Extended magazines can be purchased from the Military Shop in the Campaign pause menu. However, unlike in Multiplayer, magazine capacity is doubled for all weapons except for launchers. This is ideal for weapons such as the MC81 or the Automat-X, which are prone to run out of ammunition at awkward moments.
Extended magazines are available for all weapons except for launchers for 2,000 credits. However, unlike in the Campaign, magazine capacity is only boosted by roughly 50%. Regardless, this is still a convenient attachment for weapons with smaller magazines. As such, it is one of the more common attachments used online.
Extended magazines cannot be paired with FMJ rounds.
The extended magazine returns in the multiplayer for Modern Combat 4: Zero Hour, however, all weapons that have this attachment equipped will have their mobility cut down by 5% and the reload speed is slower by 15%. This attachment greatly benefits automatic weapons with low magazine counts, like the SOCAR-S A1 and the VECT9, but it is less useful on weapons with a large magazine, like the Charbtek-28.