This is just one way of doing it. You might also get away with it by simply extruding a box and shaping it into the shape of the dustcover. But I personally like manually placing vertices and building the faces between them when I'm working with complex and irregular shapes.
It might look like it'd be a lot of work to do it this way, but its actually quite fast.
This is not entirely how I'd do an object like this. but I'll be trying to get through as many different modeling techniques as possible, to show off the different methods you can work with.
We start by putting a good reference picture in as the background of a viewport. then we create a simple box anywhere in the world.
Then use edit mesh and manually create vertices along the edges of the reference picture (where ever you can see there is a shape change in the reference)
When done it should look something like this
Now add the depth of these verteces. the VAL dust cover slopes a bit toward the top where it becomes round.
Now its time to build the faces in between. It might take a little while getting used to creating faces so they are connecting the correct vertices without having sharp bends or are facing the wrong direction.
The general rule is to place a face so that it is as big as possible, and avoid getting super thin and stretched faces.
When done building the faces, you should have something that looks like this.
Now copy and mirror that side of the dustcover. delete the part of the mesh that is around the ejectionport, and rebuild it according to what the other side of the gun should look like. In this case you can dublicate the rear buldge and move it forward to each of the forward buldges (sorry I didn't get more pictures of this process)
After that attach the mirrored object to the main object.
It is important when you work with objects that have been mirrored that you select the non-mirrored object and then attach the mirrored one to that.
3d max doesnt handle mirrored objects very well, and they often mess up when put into games.
So when ever you have mirrored something, create a new object and attach the mirrored object to this object (and then delete the mesh of the object you created in case you dont need it)
When you have the two sides attached to each other, start building the faces in between.
Now select the faces of the cross-cover buldges and extrude them.
Then narrow down the extruded parts.
Weld the lower set of vertices together like so.
select the top buldge faces
and extrude them like you did with the cross-buldges.
Now we want to smooth the edge of the rear part of the cover, so we select the rear faces.
and likewise extrude and narrow it.
..continued in next thread...