Season 1 Reload dropped and this SMG is waiting for you
HOW TO UNLOCK "HRM-9" I MULTIPLAYER GUIDE (Modern Warfare 3 Tutorial)
With this Call of Duty Modern Warfare 3 Season 1 Reloaded update, there is a list of new items, weapons, and other goodies that you can unlock, battle, or otherwise easily obtain.
One of your best options, if you want to improve your game, is the HRM-9 submachine gun.
This is a very reliable submachine gun that is very versatile, with lots of tweaking options for all playstyles.