That modeling unbreakable is..... well
(the model itself is good, but the way you got there is not)
You shouldnt have a complicated mesh like that with a gun. Remember you dont want triangles. They cause weird lighting errors on the mesh, and when animated look horrible.
Polygon extrusion is the easiest way in my opinion. You can draw in points where you need, and extrude anything to get the shape of the gun, and get a low poly neat mesh too. xsibase.com is where you need to be!!!
Drawing linear for the side of the gun, then welding polys in is a HORRIBLE practice. So dont do it!!
Read about polygon extrusion and implement it in the model. You will find its quick, easy to work with, and you dont need to worry so much about the mesh's points converging with one another.