Exporting problems - Black Ops 3 models

Hey guys, so I've been working on a set of custom animations for the SVG-100 sniper rifle from BO3. Initially, I received the model as one whole mesh, which was fine as I could weight-paint it (though that was a tough job). I was able to make and export all the anims with no problems whatsoever, but I got the "too many verts" error when trying to export, which I guess was caused by the model being so detailed. Simplifying the model wasn't an option as using that tool would fuck up the mesh beyond all recognition.
So the solution I tried to use was to select the mesh, then use Edit Polygon > Separate to split it into a whole bunch of pieces, and then combine them into about 12 pieces to hopefully eliminate the error and make re-rigging easier. It seemed to work, but there were two main problems that I have no idea how to solve. When trying to press 5 for smooth shading, Maya would crash for certain meshes such as those of the clip and main gun body. Also I would get this error when trying to export the model into .XMODEL_EXPORT format:
Error: Internal failure: C:/Users/Colin_2/Documents/maya/projects/default/scenes/BLACK OPS 3/SVG-100/viewmodel_svg100.mb.XMODEL_EXPORT

Does anyone know what these errors are, and how to fix them?
If not, are there any possible alternative methods to fix the "too many verts" problem?

Maybe some memory issue with Maya?

It's possible, I have a laptop with 6GB RAM and an Intel I3.

Either way, maybe I should upload the file and see if it throws the same error on someone else's computer.

EDIT: This is the model (for Maya 6.0) - https://www.dropbox.com/s/hmliko0lcz...svg100.mb?dl=0

It's loading fine and I can see it in shaded/textured mode, but in outliner I found out that (you) made a lot of polySurfaces? And whilst testing to delete them my maya crashed. (2012) So I think it's either your laptop or your maya version.

https://i.gyazo.com/e72ce88d8bae98f7...504ef95478.png

As for the too many verts error, well xmodel has iirc like a limit of 4096 vertices per group/objects (CoD1, idk CoD2+) so yeah the only way is kinda to seperate them into multiple objects.

If you did add those polySurfaces, could you instead upload the original file?

I'm at school currently, so I'll upload the original file later.

And yes, I think I made the polysurfaces. I don't know if this is the only method for Maya 6.0 or if I'm googling the wrong terms, but the only way I've found is to select the mesh and then use Edit Polygons > Separate, then combine the pieces I want. If there is a proper method to separate a mesh into new pieces, it would be nice to know.

Here's the original model in OBJ format: https://www.dropbox.com/s/f5mcq6r9eo...vg100.obj?dl=0
It works fine going from Maya to .XMODEL_EXPORT, but Asset Manager will throw the "too many vertices" error.