The Cobra fires some type of powerful high explosive incendiary round that explodes upon impact (judging by the lack of substantial recoil, this is likely some form of low-pressure grenade).
Capable of turning a car into a fiery coffin, destroying a shop facade or blowing a hole clean through a fire hydrant, the Cobra is a military grade anti-material weapon intended for use against armoured targets. The Cobra is fitted with a large electronic sighting aid and is portable and simple enough to be carried and operated by the individual soldier. When it comes to anti-structure, anti-armour or anti-vehicle operations, accept no substitute.
When Clarence Boddicker and his gang are asked by Dick Jones to kill RoboCop, they are provided with these weapons. Boddicker memorably tests the weapon by firing it at the 6000 SUX sedan leased to Joe Cox by Jones, destroying the vehicle (much to Cox's chagrin).
After RoboCop and Lewis take out Boddicker and his gang, RoboCop takes one of the Cobra Assault Cannons (presumably, the same one used by Lewis) to the OCP office building and uses it to destroy the ED-209 out in front.
Robocop uses a smaller, more compact (for an anti-material rifle) Cobra in Robocop 2 to attack RoboCain. It is less powerful, but as Robocop was using it in close proximity to soft, easy-to-puncture civilians, this was probably a tradeoff he had to make.
Behind the ScenesEdit
The Cobras are actually older-specification Barrett M82 "Light Fifty" long-range .50 BMG rifles, dressed up with extra plastic housing over the receivers and fitted with gigantic scopes.
The large sight atop the rifle was originally going to house a computer generated targetting system, but due to budget restrictions, it was shelved.
In Robocop 2 it is based on a different make and model of rifle, and lacks the original Cobra's large electronic sighting aid.