This is the msh extractor utility
(The link is inoperative)
You might also need this viewtopic.php?p=22217#22217
I would not worry about applying textures yet.
The first challenge is to create an untextured 3d model.
For a 90mm barrel maybe reduce to a 5 sided cylinder.
Using the cylinder primitive in max this will be automatically "smoothed" correctly.
Depends how close it will normally be seen in the game
Convert to "Mesh" and delete the cap from the end which will not be seen.
Select the vertices at one end and using the scaling tool to create the barrel taper, if it has one.
The start point for any accurate model is to obtain some good blueprints and crop these to just show the parts you are interested in.
Then you need to set them up in max.
http://www.onnovanbraam.com/index.php?t ... int_setup/