The MK 13 is the third part of the USSOCOM SCAR weapon system. A single-shot pump-action weapon with rotating locking breech, the MK 13 is an enhanced grenade launcher module that accepts all NATO-standard 40x46mm low velocity ammunition. It also has the inherent strength and action length to handle the enhanced medium velocity grenades with greater range and larger payloads that are now in development. Along with the multiple-strike trigger feature, a chambered defective round can be discarded by removing the entire barrel assembly and replacing it with a new barrel, allowing the operator to continue with the mission. The MK 13 may be quickly mounted underneath either the MK 16 or MK 17, or it may be configured as a stand-alone launcher with a telescoping buttstock. Like these two new FN rifles, it is a completely ambidextrous design and may be fitted with either a traditional leaf sight or mechanical quadrant sight.