So for anyone who likes to play a run and gun game (ALWAYS BE MOVING) here's a fun setup. Create a custom class, empty primary weapon and set secondary to the MOG 12 and set your perks to whatever. Then play a few games of hardcore TDM or other HC games to level up your gun, leveling guns is easier in hc mode since 1 shot = kill. Level the MOG to level 10 max in HC, it'll take 1-3 hours. Keep adding attachments as you level up.
Once you level it to max (level 10) you should have FIVE attachments on it, no optic, and zero perks. Set the attachments as long barrel, barrel choke, fast mags, rapid fire, and stock. Set your gear to acoustic sensor. You are a slaying god now, the perk gives you a really good idea of where people are (it pings the map in normal, not just sound) and the gun is insane with all the attachments. I've wiped out entire teams on TDM by running and gunning. It is a short and mid range gun so you are fucked going down long halls, just stick to corners and anything that is 20 feet or longer, don't run down or you will die. You will generally want to ADS but acoustic will let you know when to run and when to ADS.
The funny thing is the shotgun sucks balls with just 1-3 of those attachments, but once you get all 5 its a one shot murder machine. Not my gunplay but you get the idea