The MX9 is a strong close to medium range submacine gun that can be used to flank enemies and catch them by surprise. The MX9 tends to run out of ammo after a few engagements and you will get affected by enemy equipment when you get close to them. Maneuver the map avoiding most medium and long range sight lines to avoid being outclassed by assault and sniper rifles.
MX9 Best Attachments
At medium range you will want to be a target that is hard to hit. Use the stock to increase movement whilst aiming down the sights. To avoid running out of ammo too quickly use hybrid mags. Long barrel extends the range of the MX9 helping you out when you get caught by assault rifles.
MX9 Best Gear
Use the stim shot to heal quickly. Remember that you can keep shooting from the hip whilst using the stim shot to heal.
MX9 Best Perks
Flak jacket reduces the explosive damage you take letting you avoid some enemy traps. Cold blooded makes you less vulnerable to enemy scorestreaks and equipment so that you are protected whilst flanking. Ghost keeps you off enemy UAVs so that your position is not revealed prematurely.
MX9 Best Class Setup
Here is the complete best class setup for the MX9.