This achievement is tied to the fourth Pinguin side-mission.
As with the other 3 weapon cache missions you will get a call from Nightwing pretty late into the story (actually you have to choose the mission via the mission menu to get it. You will see the word "intel" under the symbol when it's ready).
Again go to the location of the goons' car, place a tracker on it and knock on the backdoor.
Start following them by gliding over the rooftoops of Gotham City. At some point they will think they have lost you and will head right to their base.
When you arrive at their base take your car with you and head inside. Shoot the goons with the weapons. head upstairs and interact with the device on the wall. Go back to your car and use the grapple hook on the engine like thing next to the gate to lift said gate.
Head inside and take care of the goons. place some explosive gel on the cache in the vault, close it and blow it up.
The achievement will unlock right away.
If you need more help refer to the video below:
(video credit: Kicknazz Games)
Hope this helps you guys :-)
Any improvements? Please let me know in the comments below!