The 10mm SMG is most effective at close-range by unleashing a hail of bullets. However, the SMG is significantly less useful at longer ranges unless assisted by the perk Concentrated Fire. The SMG simply has too much spread to be of much use beyond close-range combat. Another downfall of the SMG is its ammunition consumption; if ammunition is not properly managed, the SMG can eat through 10mm rounds at alarming speeds. With full automatic fire and a 30-round magazine, the SMG is a decent emergency sidearm against most wildlife and unarmored humans, particularly given that 10mm ammo is one of the most plentiful in the game. The SMG is also quite common, making it easy to repair and is recommended to lower level Small Guns users.
Sydney's 10mm "Ultra" SMG - Relic hunter Sydney's weapon of choice, the Ultra SMG holds an astounding 50 10mm rounds in a single magazine, and deals more damage than the standard SMG.
Sim version - A sim-only version of the weapon which differs only in health, with a whopping 999,250 hit points. Essentially preventing the gun from ever degrading, well over 1500 rounds of ammunition can be fired without it degrading 1%. The weapon is not accessible outside of the simulation without the use of the Gary 23 exploit or console commands. It can be obtained in the sim through certain equipment packs on the equipment terminal.
10mm Alloy Steel Submachinegun - Another version of the weapon was cut from the Operation: Anchorage add-on. Called the 10mm Alloy Steel Submachinegun, it is otherwise identical to the standard 10mm SMG.