From The TimeSplitters Wiki

Just a machine gun. It appeared in Khallos Express as a single and a Double. It is the worst machine gun in Timesplitters: Future Perfect. Although, when in Double form + a Max Damage power-up, it can wreak havoc.

The Machine Gun is an SMG with a very high RoF. In contrast, the accuracy and power are relatively low, especially in comparison to the K-SMG or the Soviet Rifle. The Machine Gun has only one firing mode, but it can be dual-wielded.

It only appears in TimeSplitters: Future Perfect. It makes its first story mode appearance in "The Russian Connection". It bears a very obvious similarity to the Heckler & Koch MP5K.