Go to polygon sub object, turn on Ignore backfacing. We now need to delete the unnecessary polygons. How the model looks from the side where we deleted the symmetrical parts How it looks from the other side. But if you make backup saves after each finished stage you can just load the previous stage and redo the rest from there. Now its time to split it to parts and planar map it.
Lets start with the main gun part the side of the machinery and the handle.
If we any how do detach them as one part some parts of the skin will look strange. The idea of detaching these parts is to make them face one specific viewpoint so that we can make it a 2d bitmap and paint it. So because of that we have to make more objects. Then do the same to the clip. Select the big circle in the front, detach, select the next big circle from the front, detach, select the third and last circle from the front, detach.