In this video guide I will show you how you can destroy your first convoy leader. Now first off these are random so you will need to pay attention to your map from time to time when you are in it. These seem to not pop up very often so if you see one I would say go for it quick before it disappears.
Now when attacking a convoy you will need to take out the escorts first. While taking out the motorcycles in the rear, I would suggest using the dodge button (Y) to get progress work on the off balance achievement at the same time.
Now while taking out the other escorts you will also be working towards your bytesize takedown achievement. Just use only a few rockets here unless you have plenty to spare. Make sure you hit the ones with shields if you use them. Then finish them off with the machine guns.
Once you take down the escorts you will be facing the convoy loader. You can use rockets on the convoy escorts but if you have them I would save them for the leader to make it quicker. Keep shooting him and you will be given a tutorial on weak points. Just shoot the sides that are now exposed and he will fall shortly afterwards getting your achievement.