After trying to grab this achievement, I noticed that no matter if I land all five of my RPG-7 shots into the critical spots. The achievement doesn't popped until I tried shooting all five of my rockets into one critical spot.
My recommendation for the fastest way to get this achievement is to bring a scoped RPG-7 to the new area and play the 200m mini-game with the target vehicle, a little tip to use the scope is that the 2 number of the cross hair will be most accurate, once you start the game in the building.
I suggest shooting down the engine and waiting for the target vehicle to come to a complete halted. Afterward you can now dump the next four rockets into the engine of the vehicle and then the achievement should pop for you.
This is my first time making a guide so I'm sorry if everything look messy but I wanted to help anyone, who's hunting for achievement, to save time since it took me an hour to learn how to shoot the RPG-7 and replaying the mini-game multiple times to experiment with the critical spots and its correlation to the wrecker achievement. Anyway, I'm done ranting. Hope this small spiel helped you all.

TL;DR

Hit the same critical spot, five times.

Edit 1 for Hotfix 1.0.8

Look like they did an achievement fix so this guide most likely is obsolesce but I'll keep the guide up in case people still having trouble.