Not just down the barrel, thats just a single part of it.... Anywhere that fired gases come into contact with metal, the piston, gas tube, bolt face and carrier. All of that needs wiped off, any liquid will dissolve and remove salts, Windex just has ammonia that can over time remove small amounts of copper and carbon. Super hot water is preferred.. it removes the salts, heats the metal and flash dries, so rust won't form.
As for obsolete, whats this toads definition of obsolete... I mean to me 10.4x38Rmm Swiss rimfire is obsolete, I can't find it any where.. Sure in some way x39 is obsolete, why would both Russia and China moved on to other calibers, world wide demand for x39 makes it profitable and worthy of high production, you don't cut a cash cows throat. Quit making it, there is gonna be alot of pissed Arabs, African militarys, basically anyone military who ain't a NATO suck butt will be pissed.