I'm surprised to see a thread about best Plunder load out and everybody is using accuracy or re-load speed mods on their guns. The two most important things to have in your loadout for Plunder are Back in the Saddle and Call Out mod on your gun....even more important than Beast Mode.
With all 5 members of your team using callout, the other team is constantly called out the entire game. It's like everybody on your team has Gotcha! active the entire game. Since you know where every member of the other team is, you know when to move the idle, where the enemy is coming from and where to cut them off to allow safe passage of the treasure to the box. It's the ultimate offensive tool for Plunder. Back in the Saddle is the ultimate defensive tool, self explanatory.
Back in the Saddle
Quick Boom (Mega Bombs and Clusterbombs can be thrown back allowing them to be used against your team, effectively making you responsible for killing your entire team allowing the opponent to score uncontested while you're all dead)
I use Revolution M9 with Reload Speed, Drake's Para 9, Beast Mode, Depot (that Booster that makes you become more Cash for Medals) and Speedy G.