How to get the most ammo for MM/HM

Let say we have an m60 100/100
MG mag bumps it to 100/200
Finally Mutation megazine add 50% of that 100/300

Correct me if I'm wrong but MG mag + mutation mag can get u the most ammo for machine gun in MM/HM.

I'm asking if there is another way to increase the ammo count even further?