This is a guide on how to unlock the LACHMANN SUB aka the MP5.
Modern Warfare II is out now and the Gunsmith has had a huge overhaul. The way in which we unlock weapons now has completely changed. A few still follow the traditional route and can be unlocked via simple leveling up. But, other weapons require you level specific guns first, this includes the MP5.
Firstly, it's not called the MP5 anymore, its now known as the LACHMANN SUB (likely due to copyright issues) to unlock the LACHMANN SUB you need to follow the weapons family tree. Starting with the LACHMANN-762.
Unlocking the LACHMANN SUB
LACHMANN-762 (Battle Rifle)
The LACHMANN-762 is a single fire weapon that is found under the Battle Rifle tab. Get it up to level 13 to unlock the next receiver. We didn't enjoy leveling this one.
LACHMANN-556 (Assault Rifle)
You'll then need to repeat the process with the LACHMANN-556, getting it to level 12. This was a far more enjoyable experience than the sluggish 762 grind. You'll find this one in the Assault Rifle tab.
Now that you have leveled up the 762 and the 556 you can now use the LACHMANN SUB. You'll find it unlocked in the Submachine Gun tab.
LACHMANN-762 (level 13) >> LACHMANN-556 (level 12) >> LACHMANN SUB
The LACHMANN SUB is one of the best SMG's in the game and has always been a fan favourite. Follow the steps above and it's all yours.