KJW M4 in Rifles (Gas) Posted July 11, 2010 · Report reply Are you lubricating the BCG? If so, don't. The silicon or whatever lubricant you use can really screw with the hop-up. So is it recommended that one should use non-lubracated gas. Because personally never relubed my gun, but over the course of a day after using green gas, oil will tend to seep out of the reciever. Will use of green gas also translate to oil being sent down the barrel? If the problem is due to the use of green gas, im assuming I should stick to either 134 or Propane.