Objects move around when imported

I modeled a Splatoon-like weapon in Blender, and I am trying to import it into Unity. In Blender, it looks fine. But when imported to Unity, all the parts of the weapon move around and get disproportional. Here are the images in Blender and in Unity:

 

How are you importing into Unity? I usually manually export an FBX, and before that I make sure everything is parented correctly and apply scale. I also fix the 90 degree x rotation issue before exporting so things get imported with a clean hierarchy, with no scales or rotations on any objects.

I can't say I've ever seen this exact problem though, so you must be doing something differently.

 

I'd say that the splatoon gun object you modelled in Blender, was made up of separate parts. Am I right?

As UziMonkey asked, did you join or parent, all of the object pieces in Blender, before exporting to Unity?
If not, that might explain, why the pieces of your blaster, separated from each other, after importing into Unity.

Tip: When making fancy objects like these, it is normally better, to make the splatoon gun from one mesh object
extrude faces, pull vertex points etc. than use separate mesh objects, to make one object.
That way, it would be easy for you to import your creations, into game engines, without much hassle.

But then again, according to the type of game you are making, cases do vary.
And probably, that's why you went with separate meshes, instead of one whole object.

However, doing it way you did it, (making it many/few separate objects) is also good.
Especially, if your game has the option, to change or create, or customize the look, of your splatoon blaster thingy.
eg. change the gun handle, change the gun barrel etc.

By the way, nice splatoon gun dude.