Exactly Shibi Viv said he bought the complete upper,but he built the lower.....soo...its prolly the wrong spring/buffer combo in conjunction with an A2 stock.....although the upper can still have a gas leak or a torqued up gas tube
Viv break open the rifle...point the muzzle down and drop the bcg....it should almost go into battery.
Yes a new gun can be tight,but ive built 7 of these and have never had to drip oil over the place...wet yes,but geez it doesn't take much :) Wash