Destructible Meshes only use a single Convex hull for their collision, so you cannot get the same accuracy for collision with these as you would for a static mesh. We have a feature request in for this, but It’s probably going to be a while before anything with destructibles is worked on. It’s something we want to do, but it’s just not a priority at this moment.
A workaround you can use is to have your static mesh swapped out to a destructible on hit and then apply the damage at the impact point so that you get the accuracy in collision if you really need it and still get the destructible actor that you want as well. If you’re unsure how to set this up, try searching the forums and AnswerHub. This has been covered a few times. I remember JohnAlcatraz doing a similar swap with some static meshes and destructibles that may help.