Here is the model I have for a low poly game that I am making is it possible to make a more precise collision box for it, I have tried the most complex and it still isn’t good enough.
You can use complex as simple in the complexity drop down in the static mesh, which should use the entire static mesh as collision.
The engines automatic collision has trouble with convex shapes. You could create a collision mesh for your model in your modeling software.
Check out this link:
https://docs.unrealengine/latest/INT/Engine/Content/FBX/StaticMeshes/index.html#collision
Here are three ways how you can create a collision: 