XM307 & XM312

The XM307 & XM312 were two weapons developed as part of the US Military's cancelled Objective Crew Served Weapon (OCSW) project, a subsection of the Objective Force Warrior plan which was intended to supplement or replace existing stocks of M2HB heavy machine guns and Mk 19 grenade launchers. The XM307 was also known as the Advanced Crew Served Weapon (ACSW), and fired a 25x59mm computerized HEAB round; a lower-velocity 25x40mm version of this round was used by the Heckler & Koch XM25 and was used by later versions of the equally ill-fated Heckler & Koch XM29 Objective Individual Combat Weapon. The XM307 was able to be converted to the .50 BMG XM312 configuration or vice versa by swapping a small number of parts, in a operation taking a trained crew less than two minutes.
The weapon's "differential firing" recoil-offsetting system was similar in concept to API blowback, but used the barrel and more or less the entire action of the gun instead of just the bolt as the recoil-offsetting component, working rather like a Heckler & Koch G11 in reverse. The barrel group was released from the rearward position to travel forward as the weapon fired, forcing recoil to arrest the forward momentum of the group before it could have further effect on the weapon. The XM307 was gas operated, while at the time of cancellation the XM312 was using a weird hybrid system with recoil-operated feeding but a gas-operated bolt. While this resulted in high accuracy and low felt recoil in a system much lighter than the Browning M2, it also resulted in a low rate of fire (260 rpm); this and issues with meeting the system's 40-pound weight goal led to the project's cancellation in 2008. A follow-on program for a lightweight M2 supplement, the XM806, used some of the technology used in the XM312 and succeeded in removing the gas-operated bolt; this project was itself cancelled in 2012 following delays and criticism of the XM806's still-low rate of fire (265rpm), in favour of upgrading existing stocks of M2s. Only two parts of the XM307 program survive: the first is the 25x59mm high-velocity round, which is planned for use in the Barrett XM109 Objective Sniper Weapon or "Payload Rifle," though the current status of the XM109 project is not clear. The other is the lightweight tripod used on the XM307, XM312 and XM806, which went by the name XM205. With some alterations, this has been adopted as the M205, and is planned to replace the heavier M3 tripod used by the Browning M2 and Mark 19 grenade launcher.
The General Dynamics Lightweight Medium Machine Gun uses a variant of the same recoil-mitigating technology, and appears to have finally solved the rate-of-fire issues that killed the XM307 / XM312 and the XM806.
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==XM307 ACSW==
===Television===
Show Title 	Actor	Character	Note / Episode	Air Date
Future Weapons	 	 	 	2006-2008
===Video Game===
Game Title 	Appears as	Note	Release Date
Battlefield: Bad Company 	 	 	2008
Battlefield: Bad Company 2	 	 	2010
==XM312==
===Television===
Show Title 	Actor	Character	Note / Episode	Air Date
Future Weapons	 	 	 	2006-2008
===Video Game===
Game Title 	Appears as	Note 	Release Date
Splinter Cell Chaos Theory 	 	as part of a sentry gun	2005
Ghost Recon Advanced Warfighter 	 	 	2006
Ghost Recon Advanced Warfighter 2	 	 	2007
Battlefield: Bad Company 	 	 	2008
Army Of Two 	 	used on the hovercraft 	2008
Battlefield: Bad Company 2 	 	 	2010
Blacksite: Area 51 	 	 	2010
Army of Two: The 40th Day 	 	 	2010
Category:Gun
Category:Machine Gun
Category:Grenade Launcher