Police arrested a 19-year-old university student for building and selling pen guns capable of firing 7.65 mm rounds on Monday.The suspect, identified as N.M., was detained at a bus station in the northwestern city of Bursa.He had arrived from Istanbul where he is studying mechanics.A total of 16 guns were found in his possession.The suspect told police he also worked as a lathe operator and was in Bursa to contact potential buyers.