ok but can i ask how do you get up to the room where the army proofs go without having to hang the shotgun bk up where is origonally was? i tried going bk up the elevator but its stuck on the upper floor can someone please help and give me directions?????? thanks

When you go into the elevator take it to floor 1F, when you're on this floor, turn right at the fork you will encounter and use the door at the end of that hall. You're now in the model room, all you need to do is plant the three proofs in the hole beneath the secret compartment, this will cause some Laser Beams to deactivate which will give you access to a lever. Pull this lever and a secret passage will be revealed, the one that Alfred mentioned in the 'Secret passage note'. Take the ladder down after collecting some supplies into the Waterway passage.

You should be able to take it from there...