a second thought about this brings me to the conclusion that the best solution is scaling down the weapon to the size it really has in realworld. then attach it very close to the camera as if camera were your eyes and the weapons were in your hands. you will get problems with the weapons otherwise, because they are much too big (like a house). how would you place the shooting fire if the guns are moving? how would you apply a lightsource to the weapons model etc. all this will not work correct if the gun is big like in your screen.