If you're like me, you're probably noticing that sprinting into riot shield enemies doesn't always knock their shield loose.
Luckily, you can ignore all that and get it another way.
To obtain it quickly and easily, fire up a co-op mission on Scandinavia, on Normal. In the first segment of the stage, before the first checkpoint, an APC will appear. If you're looking at it from the direction you came from, a Sergeant class enemy will appear on the left carrying an electron mace. Wipe out the enemies, grab the Electron Mace and move into the next area.
The next area will have a total of 9 shield bearers in it, before you reach the checkpoint with the UGV. Just electron mace them and they'll drop their shields, which counts towards this achievement.
Since you can get 9 in one run, you can get this quickly and easily. Be aware of snipers and/or large (semi-randomized) groups of dudes who bust out of some containers. They might put you down pretty quick.
Rinse and repeat this three times and you'll have your achievement.
Like most of the achievements related to "Do X of Y" in this game, there is a numerical stat you can check your progress on for this. This particular one is represented by the entry labeled "Shields Dropped" under the statistics page.
Unfortunately this isn't my original idea, credit goes to Sourman145 of X360A. Just thought I'd let others know.
Original post here:
http://www.xbox360achievements.org/forum/showpost.php?p=4914...----------------------------------------------
Edit: Some people have been having issues with it saving.
To save the credit towards this, you must reach the next checkpoint. That is, go forward and power up the UGV, and have the next door open. Then it will save the progress to your stats sheet.