i just found out a cool little trick to being able to shoot after the end of a game - and it does work.
All you need to do is when the game ends (normally - no nukes), and the points are almost there (td, domination..) all you have to do is have the leaderboards up (select for ps3), and there you go. I have only played around a little bit with this, but so far i can confirm that you can use your gun, and any nades/stuns/etc. This might get you that last kill you need, or possibly even lead to a bigger glitch, but im not sure. Have fun and play around with it....
I think someone else posted a glitch where you can run around knifing people after the game has ended, but you receive no credit / points, same thing probably applies here.