I don't believe "asTRa" is used to refer to all weapons in samskRtam. A sword is certainly not called an "astRa". There is no reference in Mahabharata or Ramayana of any weapon of that kind being called an astRam. All the words like "brahmAstRa", "pASupatAstRa", "nAgAstra", etc, are all for launched weapons. They are all "kinetic" in nature and are not held in hand during the fight. I believe "varuNAstra" sends some torrential rain/flood, "nAgAstra" sends something that becomes a snake when it strikes, "AgnEyAstra" sends fire, and so on. Typically, they all needed the right mental-software for a correct launch and strike, and the software were the proper mantRAs (that help the mental focus on the physics equations that defined the associated properties - which was basically called a "God" later - bramha, varuNa, agni, etc).
In fact, if I am not mistaken, a weapon that does not leave the fighter's possession or hands is called a "SastRa" (short first syllable; not "SAstRa" which is "science"). That is why the word "astRa-SastRa" is used to refer to weapons in their totality. A sword or knife is a "SastRa". That is also why surgery is called "SastRa-kRiya"....
Speaking of weapon-launch software... now, if only we could figure out a proper mantRa for a "phedereRAstra" that sends the most effective serves across the net using mental focus on the proper kinetics coming from the God "phedereR"..... No "isnErAstRa" or "grOthAstRa" please. They are speedier but not always as effective. "sAmpRaSAstra" would be good too.