On your action phase, move up to your target, round his cover. Then fire your bullet.
And if you are employing RG4: Alternate Initiative, if you are fast enough you might even be able to move away again on your second IP and take your own cover before his buddies can respond. :p
Then again, the act of
running actually act like cover....
(...then again; if you only spend a simple action shooting bullets at your target you still have a simple action to Take Cover)
Partial Cover:
Cost a simple action
Ranged attackers have +/-0 modification to hit you
You have a positive dice pool modifier of 2 dice to avoid getting hit.
Good Cover:
Cost a simple action
Ranged attackers have +/-0 modification to hit you
You have a positive dice pool modifier of 4 dice to avoid getting hit.
Running:
Cost a free action
Ranged attackers have a negative dice pool modifier of 2 dice to hit you
You have a positive dice pool modifier of 2 dice to avoid getting hit.
Melee characters even get a positive dice pool modifier of 2 dice to attack while running...
(SR5 is very melee [and gyromount] friendly)
