MAYA: Constraint or Bind? Which one should I use?

I’ve made a gun model wit ha skeletal rig - no hands, just the gun model. I wanted to animate the run cycle and since the gun is a rigid model as opposed to skin, instead of binding, I used Constraint. When importing the model I get

Warning Could not find the bind pose. It will use time 0 as bind pose.

Does parenting the objects to bones work with unreal engine or can you only “bind” the mesh?

I’ve just tested something and apparently yes, you need to use bind to attach objects to bones. Parenting or constraint seems to be just a Maya specific rigging tool.

Did you manage to figure it out? How do you bind them without getting the mesh to deform, so it acts like a mechanical object?