This trophy is cumulative so it does not need to be done in one round.
The best place to grind this trophy out is in the Beta Arena under the Survival game mode. A turret will normally spawn at least every other round. Just walk up to the backside of the turrets and tap the touch pad. If you're having trouble finding turrets, click in on the left thumbstick. This will send out a ping that will reveal all nearby enemies (including turrets).
Good luck!