I have to admit I was a little intimidated by the thought of doing this cake. After it was all said and done, I'm very happy with the end result. The definite key to this cake was in the silver food coloring spray I bought. It really finished off the cake and gave it a nice metal look to it.
I started off by making the front section of the gun (by the way, this is an AR 15, military assault rifle). The very end is made with fondant and I used a straw to carve out a small hole. The long, thin piece is a straw covered in fondant...this is the only inedible part of the cake. The black barrel was made out of Rice Krispie Treats and then covered in fondant.
The main part of the cake is the only real "cake" section. I used a template to cut a section out of a frozen piece of cake. It was much easier to cut this way. The scope on top is made from Rice Krispie Treats and each end has a rock candy piece of "glass".
All the little details on this section are made out of fondant mixed with gumtex.
The end section is also made from Rice Krispie Treats. The bottom of the black area is made with fondant and gumtex, left to dry so that it would hold it's shape.
I used a small paintbrush to add the color to the gun. I mixed a small amount of black into the silver color so that it would look more like metal.
This was not my "normal" type cake, but I was willing to take on the challenge anyway.