A pretty easy set of schematics to get are the rubber set, all you need to do is build 4 sheers (like the one you used to get to the boat in swampland) and open the 4 locked chests on the map (1 is in a random start room). you will need a lot of rubber but it's a good set to have. And regarding the gun, if you pay close attention it has a 3 burst fire followed by a cooldown that you can use to your advantage.