Once you have completed the main campaign on any difficulty, you will unlock the Museum, which can be accessed from the main menu
Now before we get into the meat of the guide, it’s very important to know the difficulty in the Museum is set by the difficulty you completed your last campaign mission on.
So for example if you completed your last mission on Veteran, the Museum’s difficulty will be set to Veteran, so make sure you go off and complete any mission on Recruit before you go into the Museum to have your best chance of surviving the attacks.
Once you’re inside the Museum, take a minute to get you bearings, check out the weapons and then have a good look around all 3 rooms, take it all in.
You see all those guys that are standing around doing their thing, they’re all going to come for you, one room at a time.
If you kill any of these NPC’s before pressing the button (we’ll get to that) you will negate your chances of getting this trophy/achievement to unlock
For me, weapon wise, I chose the ACR Assault Rifle for its’ stopping power and the L86 LSW LMG as it has the fastest reload time of all the LMG’s
But of course, this is a personal preference
Now then, let’s get to it.
Make your way to either room, I recommend the one on the right as this is the hardest room to clear.
On the counter in the room will be a red button, hold SQUARE/X to push the button then run to the middle room, get behind some cover and take the enemies down as quickly as you can.
Pay very close attention to one enemy in particular, a Juggernaut, this guy is heavily armoured, walks like the Terminator® and takes near enough a full LMG clip to his chest to take him out.
Clear the rest of the enemies, then reload, refresh (ammo box in the either room) and get ready for round 2
Same again, here, but this time the room on the left has much simpler enemies, hit the red button on the counter, run back to the middle room for cover and take them down as efficiently as possible.
When you’re faced with the Riot Shielded enemies, throw a flashbang behind them to disorientate them, then take them down before they get a chance to recover.
Once you have cleared both rooms successfully, your Trophy / Achievement will unlock