An M30 rocket is an extended-range, aerodynamically controlled, inertial and GPS guided munition fired by the M270 Multiple Launch Rocket System (MLRS). Properly, they are guided missiles rather than unguided rockets, but, since it is derived from the unguided M26, the U.S. Army has chosen to continue the "rocket" name. They are prepacked in canisters of 6 rounds, of which the MLRS can hold and fire two, for a total of up to 12 rockets fired at once. Alternatively, the M142 High Mobility Artillery Rocket System can hold one canister.
It carries 404 of the same type of cluster submunition as the M26, the M85 DPICM but to a longer range of 37mi/60km. Both the M85, and the earlier M77 DPICM bomblets, have an unacceptable "dud" rate (i.e., failure to detonate on contact), while remaining highly explosive. The duds effectively create an antipersonnel minefield, in violation of the Convention on the Prohibition of the Use, Stockpiling, Production and Transfer of Anti-Personnel Mines and on Their Destruction and a political liability.
The major application for these area-effect weapons, informally called the "grid square removal system" when a battery of six launchers fires 72 rockets, was for counterbattery against enemy artillery, although they were also effective against troops and trucks in the open. They are not effective against armored fighting vehicles. While the M30 carries fewer bomblets than the M26, its greater accuracy and range makes it comparably effective and more flexible.
Both the M85, and the earlier M77 DPICM bomblets, have an unacceptable "dud" rate (i.e., failure to detonate on contact), while remaining highly explosive. The duds effectively create an antipersonnel minefield, a treaty violation and a political liability. As a result, most, if not all, future MLRS ammunition purchases will be of the XM31, which has a unitary warhead and no dud problem.