weapon mod

how can i mod my weapons that they be stronger and got more power to kill others with outh selcting attachments ?! like mod the files of the weapons .

You can't. The files that contain this sort of data are intertwined and exclusive to each weapon's 3d model, and also can not be edited, since they are exclusive to The Call of Duty series. Until someone from Treyarch or Infinity Ward leaks the tools that they use to develop the weapon info, which is very unlikely, you will not be able to accomplish the sort of mod that you are talking about.