Best place to kill 5 summoners for rocket launcher mastery?

[Dragon1291]

Hey, guys so i am almost at end of single player mission but before i go to last mission i want to upgrade all my weapon mastery.

For other weapon mastery i used advanced research complex lab for farming masteries.

Now i am stuck as to where to farm for 5 summoner kills with rocket launcher for its lock on mastery?.

[Suina]

Start of the final mission actually spawns about 2-3 summoners in the first fight area. So you can kill them and then reload the mission to farm them