In the Red Forest do the mission to get the compass which the forester sends you on and return to him. When you talk to him, tell him you have the artifact. He will then give you a fully upgraded Vintar VC. Do not continue the conversation. After he gives you the gun, exit the conversation then talk to him again. Tell him you have obtained the artifact again. He will give you another gun. This can be repeated as many times as desired and the guns can then be sold.
Added by: Sanzano Mar 18th 2011, ID#16037