This achievement can be easily unlocked with a Limpet Grenade charge and a few rockets. Head to the La Mugre pier by the beach and find the series of explosive barrels at the end of the pier. Follow them to the end furthest from the carnival, place a charge on the first barrel, and detonate it. The explosion will travel across almost all of the barrels. When they blow up, run about halfway down the pier and look at the second floor of the large house to your left. Shoot a rocket at the door closest to you and go back to the barrels at the end of the pier, as they should have respawned by now. Keep shooting these spots as they respawn and your achievement should unlock.