Load the .nif in Nifscope. Have the Block Details window displaying. Select Render>Show All (or show hidden) from the menu. All the bips and bonding boxes should appear. Someplace around the of the character should be a little box, usually green but not necessarily. If you click on it, it should highlight the node in the Block Details and you can be sure it is the weapons node, although, I just loaded The Blob and the name is "Box". Anyway, select Transform>Edit, and you will get a window with Translation, Rotation, and Scale. Changing the number for the x, y, and z boxes will move the box around. Sometimes the box will move parallel to the axies on the mesh, other times they seem to move to some strange kind of dimensional setting that perhaps only a Galifreyan could accurately handle.