For those playing with a partner, you might not unlock this achievement at around the point Vermin360 mentions (or maybe one player will, but the other one won't).
So, for the partner, instead of going through other stages to get the achievement, go to Episode V Chapter 2: Escape from Echo Base. You'll find a gun turret not too far from the start of the level... Knock the stormtropper off the turret (by destroying it), then rebuild the turret.
Once it's built, you can destroy it again and build it again. You can do it as many times as you like, and with fast build enabled, you should get your 100 in no time.
Something I forgot to mention that Templar Punk pointed out. If you unlock the fast build option, it makes building the turret a lot faster. Also, there's a radio you can smash and rebuild in Jabba's Palace.
Happy boosting :)