Ok, host a Attack and Defend Game on Kill House. Set the respawn to one of the following: No Respawns: for the Ace of Spades achievement OR 3 respawns (the whole defense team gets Cluster Bomb). {NO FRIENDLY FIRE} Get about 6-10 players in the game, and have three people on the defense team, with the rest on the Assault team. Have the defense team loadout with Grenades and Incendiaries. Have the Assault team loadout with LMGs.
When the game starts, have the assault team gather together in a tight circle and start shooting each other with their LMGs. At the same time, the three man defense team is making their way to the circle of machine gunners. Have one member of the defense team (whoever wants the achievement) throw a grenade or incendiary at the huddle. The thrower will get XP for the kills, while the Assault team gets XP (10-12) PER PERSON for the assist.
The final time the assault team respawns, have one member of the assault team go grab the bomb and score it= 400 XP
The defense team will have to take turns and know who throws first if they want the achievement.
Happy Boosting
Multiplayer XP Glitch (and achievement)
Multiplayer XP Glitch (and achievement) 
Linear Mode
