The XM307 Advanced Crew Served Weapon is a prototype grenade launcher meant to be mounted on a tripod. It was intended to either replace or supplement the Mk19 automatic grenade launcher and the M2 Heavy machine gun. The XM307 project has been cancelled due to its significantly higher cost compared to those of the Mk19 and the M2 HMG.
InBattlefield: Bad Company's singleplayer, theXM307 is rarely seen. It can be seen used by Serdaristani soldiers during Par for the Course in a watchtower right after the big bridge along the way to destroying the first SAM sites at the very beginning of the level. It is also used by Russian enemies on Crash and Grab, mounted with a ballistic shield along the mountain path towards the monastery. It is also seen during the car ride segment in Ghost Town, where it is used by Preston on a CAV, and by the Legionnaire Mercenaries mounted with a ballistic shield. It is also mounted on to Patrol Boats and CAV buggies. It generally kills enemies in a single blast.
In multiplayer, it is seen as a mounted emplacement with a ballistic shield on certain maps such as Oasis, Final Ignition, etc., and on Patrol Boats and CAV buggies. They act similarly to under-barrel grenade launchers, only they're much more effective since it can shoot 5 grenades before overheating. It can also be used effectively against enemy vehicles, dealing a heavy payload before it has to overheat. However, it is weak in destruction, usually taking 3 grenades to blow a standard wall.
In Battlefield: Bad Company 2's singleplayer, the XM307 can be rarely found throughout certain missions as an emplacement usually used by the enemy. It is also mounted on Patrol Boats and on CAV buggies.
In multiplayer, it is found on Patrol Boats on the front and back. It has a small ballistic shield and performs similarly to that of Battlefield: Bad Company, however it shoots 6 grenades at a time before reloading. It is an emplacement on the Rush mode of Atacama Desert, added in VIP Map Pack 4. A shielded version also appears in the Rush variant of Harvest Day at the last base, and Oasis in Rush. It is mounted in defensive positions for the defenders and is usually equipped with a large ballistic shield. It is also mounted on CAV's as the second passenger's weapon.
In Battlefield: Bad Company and Battlefield: Bad Company 2, kills achieved with the XM307 on a Patrol Boat or on a CAV will count as kills for the Patrol Boat or CAV respectively, whereas kills with the standalone XM307 will count as kills for the XM307.
In Battlefield: Bad Company 2, the in-game stats menu will call the XM307 the "XM-306 Auto GL", whilst, when a kill is achieved with the XM307, it will be referred to as the "XM307".