The cobra

unlike many vehicles, the Cobra fills two distinct roles, that of a mobile Anti-Vehicle platform, and of a self-propelled artillery piece. It features armored panels that are designed to deflect hardened projectiles and absorb massive amounts of damage from explosive shells. Although it is not fast, the Cobra is still highly maneuverable, and can keep up with combat groups.

The SP42 Cobra is equipped with a pair of 16 MJ LRG Rail Guns on its turret that fire a high-density ferrous slug designed to penetrate enemy armor using sheer kinetic energy. It has a slow rate of fire, although. It also fires a projectile twice the size of a M68 Gauss Cannon slug. The rail guns fire intermittently, not in a single burst, as the energy required to accelerate the slug to the speeds required to pierce the heaviest armor can only be managed for one of the cannons at a time. Synchronized fire from both Gauss Cannons will destroy even the most heavily armored tank, with penetration that easily out-guns the standard 90mm gun of the M808B "Scorpion" MBT.

In addition to the Cobra's anti-vehicle role, the Marine tank crews can stabilize the vehicle into the ground, "locking it down", and deploy an arcing-trajectory 8 MJ LRG Rail Gun which fires a conventional explosive shell at supersonic velocities. Both the explosive and kinetic force of the shell complement each other to increase the damage inflicted.^[1] When fully upgraded with the 'Piercing Shot' upgrade, one shot on the Normal difficulty has enough power to penetrate the shield mounted on a Locust and destroy it, while one shot can disable the shield on an upgraded Wraith and deal minor damage. In addition, the Cobra, when commandeered by Spartans and after acquiring about 15 stars, is capable of destroying a Scarab in just two shots. It sacrifices mobility for the range that elevating the heavy weapon can offer. The shells used are multipurpose, and can be adapted to eliminate anything from a formation of Covenant Wraiths to an enemy fortification or firebase, though its use against groups of infantry may be less effective if they are spread apart due to its small blast radius. Cobras can attack only ground units and are specifically designed to engage vehicles, so they are mostly vulnerable to Hunters and Banshees.I have got this info from halopedia.com