When in the Red Forest and the forester sends you on the mission to get the compass, get it and return to him. When you talk to him tell him you have the artifact and he will give you a fully upgraded Vintar VC, DONT continue the conversation, once he gives you the gun, exit the conversation. Then talk to him again and tell him you got the artifact again. he will give you another gun, do this as many times as you want, then go and sell the guns for a huge profit. I made 200,000 in 10 minutes.
In the Clear Sky base there is an elevated shack that contains the faction tech. Position yourself underneath his shack and when you jump you will no-clip through the floor and if you hold 'F' you will be able to take up to 2 AKM Assault Rifles and one PSO-1 Scope.