How to correctly animate and models vehicles/weapons

I can’t find any information relating to my issue, I don’t know if modeling in blender I should group all the objects under 1 parents or leave a few out (like the magazine). And I don’t know if I should do the same for vehicles, and help would be greatly appreciated. Like should I parent the magazine to the frame of the gun I model and then just make an animation class for it or use code to spawn a magazine upon reload and attach to the hand. I am new to game design so I am trying to learn it as I go but I just don’t wanna model an entire vector for example only for it to be done incorrectly so I would have to entirely redo it.

For any parts that stick together, even if they animate over each other (like the bolt action, or folding buttstock) export them from blender as one object and then import them into unreal as a skeletal mesh.

When exporting from blender, select the objects that make up the gun, go to file > export > fbx, check the “selected objects” box, then confirm export. Animations are defaulted to bake on export, but you can check in the animation tab before confirming export (all animation tab check boxes should be checked).
When importing to unreal, make sure it’s coming in as a skeletal mesh, also make sure that “import animations” is checked and “animation length” is set to “exported time”. If animation doesn’t come in, delete the asset and reimport, change the “animation length” to another option and try again.
If unreal complains that there are multiple roots, then head back in blender, make sure you have all gun parts parented into the mesh for the main body and try again.
If it’s still no good, thenidunno.