A fairly easy boss fight if you know what to do. The trick is to stay close to him at all times. That way you will dodge his most powerful moves quite easily.
He has a few basic attacks. He will spray bullets from his two cannons on his arms. Stay right up close and position yourself directly between the cannons to avoid his fire. Don't forget to use your secondary weapon when available as this does massive damage.
When he starts spinning, move to a mid ranged position so you can easily anticipate the gaps in the different patterns of bullets that he emits.
When he starts firing missiles, a target appears on the ground where the rockets will land. Simple enough to avoid.
After 2 rotations of these attacks, he will mix bullets in a spiral pattern and missiles, but he'll go down quickly during this section so is nothing to worry about.