Great to do in coop checkpoints. You'll know the next objective is a weapons cache when its a diamond with dotted borders instead of a circle. Simply clear the area, go to the cache, and plant the bomb using
and click
to detonate.
Alternatively, you can use an explosive like a 40mm or a rocket to blow up the cache and still get the achievement, or you could use an incendiary grenade on the cache for it to eventually blow up and still get credit.