1.Go to private match and put gamemode on search and destroy.
2.Invite your mate then do the following switch lobby to combat training then circle up x up x.
3.Your mate should be in combat training search and destroy tell him to do nothing.
4.When you get on to the multiplayer menu go on private match and select search and destroy then go on edit game options-general options-live and health options and change lives to unlimited stay there.
5.Tell your mate to invite you to that same lobby.
6.Join the invite tell him to back out then you press x then circle then you can invite him back and start.

This was not found by me i found it in the forums and i posted it.