This can be boosted with 4 players in a private Free For All or Team Deathmatch. Alternatively, you can easily achieve this in Initiation B (Afghanistan) co-op mission. Once you exit the chopper, select your grenade with and start sprinting forward and up the stairs where several enemies will spawn from (around 6-8.) At this point, you should huddle up close to the enemies and cook your grenade by holding , at which point you will commit suicide and with you kill multiple enemies. The enemies tend to move around and sometimes even run away once you cook you grenade, so this may take a couple attempts.