This is the first heavy vehicle the player can use as a support vehicle, boasting better range than most support units at it's level. It isn't as powerful as five mortarmen nor durable, but it has longer range and can hit farther over obstacles. It also can outrange a railgun (whose range is 360) and is likely the first acquirable unit with such ability.
Although it takes up a lot of capacity, the M270 isn't powerful without a few more in quantity. They are still very vulnerable to other defending units as it can't hit them so try bringing in some Machine Gunners or riflemen to destroy defending Reapers and Helicopters. They can still replace mortarmen in a platoon easily due to their superior range. Try to deploy them behind friendly tank-role units to unleash havoc. Although one may be tempted, it's not recommended to use them to directly target defending enemy units as this will draw their aggro and cause them to be easily destroyed.