A write-up on how i got to this..
I found the exported models online "here" so after download it was time to make it a printable model. Here is how i did this. I used lots of tools to go from a game model to a printable part, applied lots of fixes etc. Download the model here http://www.thingiverse.com/thing:1657532
Blender (https://www.blender.org/) is uses to convert the "game" file to something i can work with in other programs, also removed the so called bones from the model with blender. You probably can do a lot more steps with blender, you might be able to do all ... its just my skill level of blender that is lacking.
add the plugin to open "game" files
import the model file
move the model to reveal the "bones" and delete them
export as STL
fixing them online
General purpace mesh editor (http://www.meshmixer.com/) again way more powerfull and capable then my skill set, but for me a easy mesh editor to make sure the model aint split up.
download and install meshmixer
separate the shells, so it can be fixed
generate face groups so its easier to select the faces
extend the selected faces
export as STL
second time repair this will now join the shells as the now overlap
So now i had some decent STL's to be able to put the model together and add some weight, i added a hole in thinkercad (https://www.tinkercad.com/) i used a peice of M12 (for strenght its way overkill but it adds a decent amount of weight)
youll be able to see the added cilinder wits is a hole in thinkercad
export the model.
Cutting it up
You'll need a really big printer if you want to print it as one piece, witch i don't. I was able to print it in 3 pieces witch are still large prints. You might want to cut it up in even more pieces (i added the full gun with and without the hole so you're able to do so).
I sliced everything with simplify3D (https://www.simplify3d.com/) as you can guess it needs a fair amount of support. I used the auto support and removed and added support manually (dont know any free software wicht allows you to do the same)
Printing the model on my brand new E3D's Bigbox (http://bigbox-3d.com/) witch i who'd recommend any day.
Printing the front
longest print so far
printing the middle
Longest print so far ;-)
looks small but its 60 cm in lenght
prepping for paint
after paint (airbrush) and glued together a few layers of satin clear