Assume that the base of a Container is the wider surface, as far as distinguishing the top from the bottom. It takes about 70 shots to kill a Container.
Torpedoes make it go faster.
It is generally a better idea to ID the Container before you destroy it. Also, don't help take down a Container's shields, so that it may be disabled, from a distance. If you are going to help in this manner, do so at close range.