You can't have two weapons in Spearhead or Breakthrough when you try it will always just drop extra weapon at your feet, do a search on TMT forums they deal with spearhead more than people here do.
took me 2 seconds to find this should give it a try sometimes
http://www.modtheater.com/threads/2-...weapons.34408/
http://www.modtheater.com/threads/al...2/#post-306453