Though a lot of the weapons used by US troops today chart their lineage to decades-old designs, they've changed a lot since they were first introduced. The M16, for instance, has gone from having iron sights to using holographic optics. The M1A2 SEP v3 is a much deadlier tank than the original M1.
The M270 MLRS is another prime example of increasing lethality and firepower over the years. When it entered service in 1982, it was designed for the purpose of removing a grid square with 12 M26 rockets, each carrying 644 M77 submunitions that it could fire at targets up to 20 miles away. In essence, it was like dropping a bunch of cluster bombs without help from the Air Force.
During Desert Storm, the MLRS performed well, often using the baseline M26 rocket. But longer-range rockets were developed that could reach out to 28 miles, and they still carried the M77 cluster munition.
Then the M77 warheads were replaced with the newer M85s, which pack the same punch, but which reduced the dud rate from about 5 percent to 1 percent. Then, the M30 gave this ground-launched cluster bomb precision guidance.
Today, though, the state of the art is the M31 guided unitary rocket. According to a Lockheed Martin e-brochure, this rocket replaced the M85 bomblets with a 200-pound high-explosive warhead. This rocket has GPS and inertial guidance systems, enabling it to hit within 30 feet of its target – and it can fire its rockets from as far as 44 miles away.
In essence, this makes the MLRS a sniper with a 44-mile reach.
Lockheed is also offering a "GMLRS Alternative Warhead" which could potentially replace the ones that are essentially cluster bombs. One thing for sure, the MLRS will be around for a long time, so who knows what other rockets will be developed.