If you've ever played Metro 2033 or Metro Last Light then you've seen the Tihar And the other pneaumatic weapons in these games and how effective they are and I'd like to build one.

Step 1: The Materials

Okay sense I haven't built one (yet) this is just a guestimation of what would be needed.
-Metal Pipe (with the seam on one end) as a barrel.
-1lb air tank to hold the air pressure needed to fire the gun.
-Piston like air pump to fill the tank by hand.
-A couple hoses
-A few one way check valve
- A Firing Mechanism (I don't know much about that stuff)
-I'd prefer it have a clip. In the game it was a small tube with 4 slits down the sides filled with 15mm ball bearings.