When you get home, take the barrel and sight (ONLY THE BARREL!!) to a jeweler and ask him to silver solder it back on. Cheap repair - will last for years. I will repeat the advice about not trying to glue, epoxy, whatever, it back on for the weekend. I tried every adhesive known to man a few years back when this happened to me. You'd be surprised how much torque fixing and unfixing the bayonet really produces; stripped the sight off every time. If you don't have the tools to do it at home, simply explain to your commander what happened. He should understand.
Pine River Boys, Co I, 7th Wisconsin
"We're... Christians, what read the Bible and foller what it says about lovin' your enemies and carin' for them what despitefully use you -- that is, after you've downed 'em good and hard."
-Si Klegg and His Pard Shorty